Like vinegar, making expert twitch (6)
I believe the answer is:
acetic
'like vinegar' is the definition.
(I've seen this before)
'expert twitch' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'twitch' becomes 'tic' (tic is a kind of twitch).
'ace'+'tic'='ACETIC'
'making' acts as a link.
(Other definitions for acetic that I've seen before include "sort of acid" , "Saucy'" , "Vinegary acid" , "Colourless pungent acid" , "Type of acid derived from vinegar" .)