Stay to drink beer (9)
I believe the answer is:
supporter
'stay' is the definition.
(thesaurus)
'drink beer' is the wordplay.
'drink' becomes 'sup' (I've seen this before).
'beer' becomes 'porter' (I've seen this in other clues).
'sup'+'porter'='SUPPORTER'
'to' is the link.
(Other definitions for supporter that I've seen before include "Advocate" , "Adherent, defender" , "One cheers" , "Fan; heraldic figure" , "angel" .)