Be extremely vocal (5)

I believe the answer is:

utter

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'vocal' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I can't see?

I don't understand the remainder of the clue.

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(Other definitions for utter that I've seen before include "(Of counterfeit money) put into circulation - say" , "Antique offer for sale" , "To say, articulate" , "Circulate" , "Absolutely" .)

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

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