The Collaborative International Dictionary of English v.0.48:

Clue \Clue\ (kl[=u]), n. [See Clew, n.]
   A ball of thread; a thread or other means of guidance. Same
   as Clew.
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         You have wound a goodly clue.            --Shak.
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         This clue once found unravels all the rest. --Pope.
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         Serve as clues to guide us into further knowledge.
                                                  --Locke.
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The Collaborative International Dictionary of English v.0.48:

Clew \Clew\ (kl[=u]), Clue \Clue\, n. [OE. clewe, clowe, clue,
   AS. cleowen, cliwen, clywe ball of thread; akin to D. kluwen,
   OHG. chliwa, chliuwa, G. dim. kleuel, kn[aum]uel, and perch.
   to L. gluma hull, husk, Skr. glaus sort of ball or tumor.
   Perch. akin to E. claw. [root]26. Cf. Knawel.]
   1. A ball of thread, yarn, or cord; also, The thread itself.
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            Untwisting his deceitful clew.        --Spenser.
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   2. That which guides or directs one in anything of a doubtful
      or intricate nature; that which gives a hint in the
      solution of a mystery.
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            The clew, without which it was perilous to enter the
            vast and intricate maze of countinental politics,
            was in his hands.                     --Macaulay.
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   3. (Naut.)
      (a.) A lower corner of a square sail, or the after corner
           of a fore-and-aft sail.
      (b.) A loop and thimbles at the corner of a sail.
      (c.) A combination of lines or nettles by which a hammock
           is suspended.
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   Clew garnet (Naut.), one of the ropes by which the clews of
      the courses of square-rigged vessels are drawn up to the
      lower yards.

   Clew line (Naut.), a rope by which a clew of one of the
      smaller square sails, as topsail, topgallant sail, or
      royal, is run up to its yard.

   Clew-line block (Naut.), The block through which a clew
      line reeves. See Illust. of Block.
      [1913 Webster]

WordNet (r) 3.0 (2006):

clue
    n 1: a slight indication [syn: hint, clue]
    2: evidence that helps to solve a problem [syn: clue, clew,
       cue]
    v 1: roll into a ball [syn: clue, clew]