Crossword Genius

Harbour we hear associated with a lock (3)

Ross

I believe the answer is:

key

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'lock' is the definition.
(thesaurus)

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(Other definitions for key that I've seen before include "Essential; solution" , "Coral reef off southern coast of Florida" , "It can open" , "Lock opener; low island" , "Crucial arch-stone" .)

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