Sounds like the fellow will get better (4)
I believe the answer is:
heal
'get better' is the definition.
(synonyms)
'sounds like the fellow will' is the wordplay.
'sounds like' indicates a 'sounds like' (homophone) clue.
'the fellow will' becomes 'hell' (he will).
'hell' sounds like 'HEAL'.
(Other definitions for heal that I've seen before include "Cure, make well" , "Cure, restore" , "Of wound, mend and get better" , "Restore to health" , "Make whole and healthy" .)