Lose temper in childish game (4)
I believe the answer is:
snap
'game' is the definition.
(card game)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for snap that I've seen before include "Break under strain" , "Spell of cold weather and card game" , "on the spur of the moment" , "Lose cool" , "Simple card-game" .)