Sour recluse is heard (6)

I believe the answer is:

acetic

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'sour' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for acetic that I've seen before include "Like vinegar's acid" , "sort of acid" , "really sour" , "Colourless pungent acid" , "Type of acid derived from vinegar" .)

I've seen this clue in The Telegraph.

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