Drive away outcast that's returned (5)
I believe the answer is:
repel
'drive away' is the definition.
(to repel is to drive away)
'outcast that's returned' is the wordplay.
'outcast' becomes 'leper' (leper is a kind of outcast).
'that's returned' says the letters should be written in reverse.
'leper' backwards is 'REPEL'.
(Other definitions for repel that I've seen before include "Fill with distaste" , "Drive back - revolt" , "Put off - disgust" , "Parry" , "Beat back; cause disgust to" .)