Punch referee's head in game (5)
I believe the answer is:
poker
'game' is the definition.
(poker game is a kind of game)
'punch referee's head' is the wordplay.
'punch' becomes 'poke' ('poke' can be a synonym of 'punch'**).
'head' says to take the initial letters.
The initial letter of 'referees' is 'r'.
'poke'+'r'='POKER'
'in' is the link.
(Other definitions for poker that I've seen before include "Jabber" , "Fire-iron" , "Fire-raiser" , "A game for the fireplace implement" , "Fireside implement - card game" .)