Because of the party, go too far (6)
I believe the answer is:
overdo
'go too far' is the definition.
(I've seen this before)
'because of the party' is the wordplay.
'because of' becomes 'over' (eg 'he's upset over it').
'the party' becomes 'do' (do is a kind of party).
'over'+'do'='OVERDO'
(Other definitions for overdo that I've seen before include "Be excessive, perhaps in cooking food" , "Perform excessively" , "Use too much of (something)" , "Exaggerate, go too far" , "Exhaust" .)