Maximum resentment, by the sound of it (4)
I believe the answer is:
peak
'maximum' is the definition.
(similar in meaning)
'resentment by the sound of it' is the wordplay.
'resentment' becomes 'pique' (I've seen this before).
'by the sound of it' indicates a 'sounds like' (homophone) clue.
'pique' is a homophone of 'PEAK'.
(Other definitions for peak that I've seen before include "Pinnacle" , "Sharp pointed summit" , "Part of cap; mountain" , "High point" , "Pointed mountain" .)