The Collaborative International Dictionary of English v.0.48:

Clearing \Clear"ing\, n.
   1. The act or process of making clear.
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            The better clearing of this point.    --South.
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   2. A tract of land cleared of wood for cultivation.
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            A lonely clearing on the shores of Moxie Lake. --J.
                                                  Burroughs.
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   3. A method adopted by banks and bankers for making an
      exchange of checks held by each against the others, and
      settling differences of accounts.
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   Note: In England, a similar method has been adopted by
         railroads for adjusting their accounts with each other.
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   4. The gross amount of the balances adjusted in the clearing
      house.
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   Clearing house, the establishment where the business of
      clearing is carried on. See above, 3.
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The Collaborative International Dictionary of English v.0.48:

Clear \Clear\, v. t. [imp. & p. p. Cleared; p. pr. & vb. n.
   Clearing.]
   1. To render bright, transparent, or undimmed; to free from
      clouds.
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            He sweeps the skies and clears the cloudy north.
                                                  --Dryden.
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   2. To free from impurities; to clarify; to cleanse.
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   3. To free from obscurity or ambiguity; to relive of
      perplexity; to make perspicuous.
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            Many knotty points there are
            Which all discuss, but few can clear. --Prior.
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   4. To render more quick or acute, as the understanding; to
      make perspicacious.
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            Our common prints would clear up their
            understandings.                       --Addison
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   5. To free from impediment or incumbrance, from defilement,
      or from anything injurious, useless, or offensive; as, to
      clear land of trees or brushwood, or from stones; to clear
      the sight or the voice; to clear one's self from debt; --
      often used with of, off, away, or out.
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            Clear your mind of cant.              --Dr. Johnson.
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            A statue lies hid in a block of marble; and the art
            of the statuary only clears away the superfluous
            matter.                               --Addison.
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   6. To free from the imputation of guilt; to justify,
      vindicate, or acquit; -- often used with from before the
      thing imputed.
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            I . . . am sure he will clear me from partiality.
                                                  --Dryden.
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            How! wouldst thou clear rebellion?    --Addison.
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   7. To leap or pass by, or over, without touching or failure;
      as, to clear a hedge; to clear a reef.
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   8. To gain without deduction; to net.
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            The profit which she cleared on the cargo.
                                                  --Macaulay.
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   To clear a ship at the customhouse, to exhibit the
      documents required by law, give bonds, or perform other
      acts requisite, and procure a permission to sail, and such
      papers as the law requires.

   To clear a ship for action, or To clear for action
      (Naut.), to remove incumbrances from the decks, and
      prepare for an engagement.

   To clear the land (Naut.), to gain such a distance from
      shore as to have sea room, and be out of danger from the
      land.

   To clear hawse (Naut.), to disentangle the cables when
      twisted.

   To clear up, to explain; to dispel, as doubts, cares or
      fears.
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WordNet (r) 3.0 (2006):

clearing
    n 1: a tract of land with few or no trees in the middle of a
         wooded area [syn: clearing, glade]
    2: the act of freeing from suspicion
    3: the act of removing solid particles from a liquid [syn:
       clearing, clarification]

Moby Thesaurus II by Grady Ward, 1.0:

137 Moby Thesaurus words for "clearing":
   Lebensraum, absolution, acquittal, acquittance, air space,
   aperture, back country, breaking out, broaching, cavity, chasm,
   check, cleaning out, clear space, clearance, cleft, compurgation,
   corn field, crack, cultivated land, defecation, depletion, desert,
   destigmatization, destigmatizing, disburdening, discharge,
   discharging cargo, disclosure, disculpation, disembarrassment,
   disembroilment, disencumbrance, disengagement, disentanglement,
   disinvolvement, dislodgment, dismissal, distant prospect, drainage,
   draining, egress, elimination, empty view, emptying, evacuation,
   excretion, exculpation, excuse, exhausting, exhaustion,
   exoneration, explanation, extrication, fenestra, field, fistula,
   fontanel, foramen, forgiveness, freeing, gap, gape, gat, glade,
   gulf, hayfield, hiatus, hole, hollow, inlet, interval,
   justification, lacuna, laying open, leak, living space,
   off-loading, open country, open space, opening, opening up,
   orifice, outback, outlet, paddy, parcel of land, pardon,
   passageway, patch, piece of land, plain, plat, plot, pore, prairie,
   purgation, purging, quietus, quittance, rationalization,
   rehabilitation, reinstatement, release, releasing, remission,
   removal, restoration, rice paddy, slot, space, split, steppe,
   stoma, terrain, territory, throwing open, tract, uncluttering,
   uncorking, unhampering, unknotting, unloading, unraveling,
   unscrambling, unsnarling, unstopping, untangling, venting,
   verdict of acquittal, vindication, voidance, voiding, wheat field,
   wide-open spaces, wilderness, yawn