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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WordNet (r) 3.0 (2006):

clearing house
    n 1: a central collection place where banks exchange checks or
         drafts; participants maintain an account against which
         credits or debits are posted