Disgust turning back to outcast (5)
I believe the answer is:
leper
'outcast' is the definition.
(leper is a kind of outcast)
'disgust turning back' is the wordplay.
'disgust' becomes 'repel' ('repel' can be a synonym of 'disgust').
'turning back' says the letters should be written in reverse.
'repel' backwards is 'LEPER'.
'to' is the link.
(Other definitions for leper that I've seen before include "sick person" , "Someone shunned" , "Person shunned socially" , "Outcast, pariah" , "Social reject" .)