Drink with dark beer fan (9)
I believe the answer is:
supporter
'fan' is the definition.
(thesaurus)
'drink with dark beer' is the wordplay.
'drink' becomes 'sup' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'dark beer' becomes 'porter'.
'sup'+'porter'='SUPPORTER'
(Other definitions for supporter that I've seen before include "sports fan?" , "Champion" , "Advocate" , "Fan; heraldic figure" , "Stay" .)