Crooner joining love game (5)
I believe the answer is:
bingo
'game' is the definition.
(bingo is a game)
'crooner joining love' is the wordplay.
'crooner' becomes 'Bing' (Bing Crosby).
'joining' means one lot of letters go next to another.
'love' becomes 'o' (love means zero in tennis).
'bing'+'o'='BINGO'
(Other definitions for bingo that I've seen before include "I've completed my card!" , "Lotto" , "Game in which "two little ducks" might be called" , "Voila!" , "game requiring little ability" .)