Back to drink wine (7)
I believe the answer is:
support
'back' is the definition.
(I know that back can be written as support)
'drink wine' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'wine' becomes 'port' (port is a kind of wine).
'sup'+'port'='SUPPORT'
'to' acts as a link.
(Other definitions for support that I've seen before include "Help; bear" , "Maintain, back" , "Bear the weight of (something)" , "strengthen" , "Bear; assistance" .)