Encouragement to drink fortified wine (7)
I believe the answer is:
support
'encouragement' is the definition.
(thesaurus)
'drink fortified wine' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'fortified wine' becomes 'port' (port is a kind of fortified wine).
'sup'+'port'='SUPPORT'
'to' acts as a link.
(Other definitions for support that I've seen before include "Bear; corroborate" , "Cheer" , "Hold up" , "used to give strength?" , "base" .)