A victory over greed (8)
I believe the answer is:
voracity
'greed' is the definition.
(thesaurus)
'a victory over' is the wordplay.
'over' indicates an anagram.
'a'+'victory'='avictory'
'avictory' with letters rearranged gives 'VORACITY'.
(Other definitions for voracity that I've seen before include "Desire for large amount of food" , "Appetite" , "Ravenousness" .)