Consumed by fury, discontented vigilante becomes agent of retribution (7)
I believe the answer is:
avenger
'agent of retribution' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'consumed by fury discontented vigilante' is the wordplay.
'consumed by' is an insertion indicator (inserted letters get consumed).
'fury' becomes 'anger' (fury is intense anger).
'discontented' says to hollow out the word (remove centre letters) (the word's contents are removed).
'vigilante' with its middle removed is 've'.
'anger' going around 've' is 'AVENGER'.
'becomes' is the link.
Can you help me to learn more?
(Other definitions for avenger that I've seen before include "one seeking to get even" , "He seeks satisfaction or retribution" , "One exacting retribution" , "One seeking retribution" , "One bent on retaliation." .)