Wicked party, sport! (8)
I believe the answer is:
baseball
'sport' is the definition.
(baseball is a kind of sport)
'wicked party' is the wordplay.
'wicked' becomes 'base' (similar in meaning).
'party' becomes 'ball' (ball is a kind of party).
'base'+'ball'='BASEBALL'
(Other definitions for baseball that I've seen before include "Lea blabs about the sport" , "US/Canadian game" , "Game played badly in the sable lab" , "Sport played with a bat" , "Game played on a diamond" .)