Abandon vermouth? Don't be silly! (4,3,2)
I believe the answer is:
come off it
'don't be silly' is the definition.
(both are expressions of incredulity)
'abandon vermouth?' is the wordplay.
'abandon' becomes 'come off' (as in coming off drugs).
'vermouth?' becomes 'it' (short for 'Italian vermouth' as in 'gin and it').
'comeoff'+'it'='COME OFF IT!'
(Other definitions for come off it that I've seen before include "Don't make me laugh" , "You're mad!" , "Don't talk rubbish" , "Stop being so stupid!" , "stop fooling" .)