Sounds like the highest point of vexation (5)
I believe the answer is:
pique
'vexation' is the definition.
(I know that pique is a type of vexation)
'sounds like the highest point' is the wordplay.
'sounds like' indicates a 'sounds like' (homophone) clue.
'the highest point' becomes 'peak' (I've seen this before).
'peak' sounds like 'PIQUE'.
'of' is the link.
(Other definitions for pique that I've seen before include "Resentment; hurt pride" , "Vexation" , "Arouse" , "Needle" , "score at cards" .)