Resentment once of failure, gone bad (7)
I believe the answer is:
dudgeon
'resentment once' is the definition.
(archaic term for a resentment)
'failure gone bad' is the wordplay.
'failure' becomes 'dud' (dud is a kind of failure).
'bad' is an anagram indicator.
'gone' anagrammed gives 'geon'.
'dud'+'geon'='DUDGEON'
'of' acts as a link.
(Other definitions for dudgeon that I've seen before include "Umbrage" , "Deep resentment" , "Sullenness" , "Anger" , "Angry feeling" .)