Look into Mafia to come back and thrive (5)
I believe the answer is:
bloom
'thrive' is the definition.
(both can mean to flourish)
'look into mafia to come back' is the wordplay.
'look' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'into' indicates putting letters inside.
'mafia' becomes 'mob' (informal term for the mafia).
'to come back' says the letters should be written in reverse.
'mob' backwards is 'bom'.
'lo' placed into 'bom' is 'BLOOM'.
'and' acts as a link.
(Other definitions for bloom that I've seen before include "Do very well" , "Orlando" , "(Come into) flower" , "Flourish" , "Flush" .)