Trendy hairstyle reportedly signified contravention (12)
I believe the answer is:
infringement
'contravention' is the definition.
(thesaurus)
'trendy hairstyle reportedly signified' is the wordplay.
'trendy hairstyle' becomes 'infringe' (I am not sure about this - if you are sure you should believe this answer much more).
'reportedly' shows a homophone (sound like).
'signified' becomes 'meant' ('mean' can be a synonym of 'signify').
'meant' is a homophone of 'ment'.
'infringe'+'ment'='INFRINGEMENT'
Can you help me to learn more?
(Other definitions for infringement that I've seen before include "Offence" , "Breaking (of a law, etc)" , "Minor lawbreaking" , "Violation of law" .)