Find out cheat exploited grief (9)
I believe the answer is:
heartache
'grief' is the definition.
(synonyms)
'find out cheat exploited' is the wordplay.
'find out' becomes 'hear' (synonyms).
'exploited' indicates an anagram.
'cheat' anagrammed gives 'tache'.
'hear'+'tache'='HEARTACHE'
(Other definitions for heartache that I've seen before include "Extreme emotional pain" , "Great sadness" , "Grief" , "Emotional distress" , "Emotional anguish" .)