What we hear is good (5)

I believe the answer is:

sound

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'is good' is the definition.
(similar in meaning)

I don't understand the remainder of the clue.

(Other definitions for sound that I've seen before include "place for sailing, perhaps" , "Not diseased or damaged - listen" , "Valid" , "Speaking" , "Healthy; narrow channel" .)

I've seen this clue in the Evening Standard.

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