Crossword Genius

Vinegary expert with a nervous twitch (6)

Ross

I believe the answer is:

acetic

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

'expert with a nervous twitch' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'with' is a charade indicator (letters next to each other).
'a nervous twitch' becomes 'tic' (involuntary twitch in the body).
'ace'+'tic'='ACETIC'

(Other definitions for acetic that I've seen before include "Like vinegar's acid" , "tart" , "Saucy'" , "Colourless pungent acid" , "in relation to acid" .)

I've seen this clue in the Evening Standard.
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