Disgust rising for outcast (5)
I believe the answer is:
leper
'outcast' is the definition.
(leper is a kind of outcast)
'disgust rising' is the wordplay.
'disgust' becomes 'repel' ('repel' can be a synonym of 'disgust').
'rising' shows that the letters should be reversed in order (going up in a down clue).
'repel' reversed gives 'LEPER'.
'for' is the link.
(Other definitions for leper that I've seen before include "Sufferer from dread disease, once made to wear bell" , "He's avoided" , "Person shunned socially" , "Someone shunned" , "Outcast, pariah" .)