Party seen to be in contravention (4)
I believe the answer is:
rave
'party' is the definition.
(thesaurus)
'to be in contravention' is the wordplay.
'to be in' indicates the answer is hidden within the clue.
'RAVE' is hidden in the letters of 'contravention'.
'seen' acts as a link.
(Other definitions for rave that I've seen before include "Rant - noisy, all-night party" , "Illegal party; talk madly" , "Pop dance party" , "Talk wildly and angrily" , "Rage" .)