Reportedly, maximum resentment (5)
I believe the answer is:
pique
'resentment' is the definition.
(I've seen this in another clue)
'reportedly maximum' is the wordplay.
'reportedly' shows a homophone (sound like).
'maximum' becomes 'peak' (similar in meaning).
'peak' is a homophone of 'PIQUE'.
(Other definitions for pique that I've seen before include "Equip (anag.)" , "Dudgeon" , "Petulant anger" , "Stimulate (someone's interest)" , "Arouse" .)