Social outcast returns in disgust (5)
I believe the answer is:
repel
'disgust' is the definition.
(I know that disgust is a more specific form of repel)
'social outcast returns' is the wordplay.
'social outcast' becomes 'leper' (someone with leprosy).
'returns' says the letters should be written in reverse.
'leper' back-to-front is 'REPEL'.
'in' acts as a link.
(Other definitions for repel that I've seen before include "Be impervious to" , "Spurn" , "Successfully resist" , "may turn your stomach" , "Drive back, rebuff" .)