Knowledge, love, for numbers game (4)
I believe the answer is:
keno
'numbers game' is the definition.
(I've seen this in another clue)
'knowledge love' is the wordplay.
'knowledge' becomes 'ken' (ken is a kind of knowledge).
'love' becomes 'o' (love means zero in tennis).
'ken'+'o'='KENO'
'for' is the link.
(Other definitions for keno that I've seen before include "gambling game" , "game of chance" , "gambler's choice" , "A bingo-like game" , "2 8 [CASINO GAME]" .)