Cool joker beaten (4,2)
I believe the answer is:
with it
'cool' is the definition.
(I've seen this before)
'joker beaten' is the wordplay.
'joker' becomes 'wit' (a witty person).
'beaten' becomes 'hit'.
'wit'+'hit'='WITH-IT'
(Other definitions for with it that I've seen before include "Trendy; in addition" , "cool" , "At the cutting-edge" , "Fashionable" , "as well?" .)