Irene ruined him (5)
I believe the answer is:
ernie
'him' is the definition.
'irene ruined' is the wordplay.
'ruined' is an anagram indicator.
'irene' with letters rearranged gives 'ERNIE'.
(Other definitions for ernie that I've seen before include "Wise, perhaps" , "Name given to selector" , "Eric's other half" , "___ Wise, d. 1999" , "Premium Bonds selection computer" .)