Player in bar with supporter (8)
I believe the answer is:
banjoist
'player' is the definition.
(I've seen this before)
'bar with supporter' is the wordplay.
'bar' becomes 'ban' (I've seen this before).
'with' says to put letters next to each other.
'supporter' becomes 'joist' (something which supports a building's structure).
'ban'+'joist'='BANJOIST'
'in' is the link.
(Other definitions for banjoist that I've seen before include "plucky player" , "Player of stringed instrument" , "plucky performer" , "Musician" .)