Clubber at event holding dress down (6)
I believe the answer is:
berate
'dress down' is the definition.
(synonyms)
'clubber at event holding' is the wordplay.
'holding' indicates a hidden word.
'BERATE' can be found hidden inside 'clubber at event'.
(Other definitions for berate that I've seen before include "Censure severely or angrily" , "Rebate (anag.)" , "Scold; angrily criticise" , "slate" , "Scold or chide severely" .)