A sound tip - go for a bit of a sail (4)

I believe the answer is:

clew

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'sail' is the definition.
(thesaurus)

I don't understand how the rest of the clue works.

(Other definitions for clew that I've seen before include "Ball of twine" , "Piece of canvas" , "Western bay" , "old ball of thread" , "Mayo bay overlooked by Croagh Patrick" .)

I've seen this clue in The Globe and Mail.

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