Unfashionable drink, we hear, not a favourite (8)
I believe the answer is:
outsider
'not a favourite' is the definition.
(I've seen this before)
'unfashionable drink we hear' is the wordplay.
'unfashionable' becomes 'out' (similar in meaning).
'drink' becomes 'cider' (cider is a kind of drink).
'we hear' indicates a 'sounds like' (homophone) clue.
'cider' sounds like 'sider'.
'out'+'sider'='OUTSIDER'
(Other definitions for outsider that I've seen before include "One not in a particular group" , "It's not among the favourites to bet on" , "1000/1 shot" , "Not a member of the group" , "Someone not accepted by society" .)