Beat banned party (5)
I believe the answer is:
outdo
'beat' is the definition.
(I know this)
'banned party' is the wordplay.
'banned' becomes 'out'.
'party' becomes 'do' (do is a kind of party).
'out'+'do'='OUTDO'
(Other definitions for outdo that I've seen before include "Surpass - overshadow - excel" , "Overcome" , "Be better in performance (than another person)" , "Beat" , "Surpass, go one better than" .)