Knocked back wine plugged by European expert (8)
I believe the answer is:
rebuffed
'knocked back' is the definition.
(to rebuff is to reject or knock back)
'wine plugged by european expert' is the wordplay.
'wine' becomes 'red' (red is a type of wine).
'plugged by' means one lot of letters goes inside another (plug can mean to block up a gap).
'european' becomes 'E' (abbreviation e.g. EU).
'expert' becomes 'buff' (buff can mean an expert or aficionado).
'e'+'buff'='ebuff'
'red' placed around 'ebuff' is 'REBUFFED'.
(Other definitions for rebuffed that I've seen before include "Rejected ungraciously" , "Abruptly rejected" , "Cold-shouldered" , "Rejected outright and bluntly" , "Snubbed, slighted" .)