Break in children's game (4)
I believe the answer is:
snap
I believe this is a double definition.
'break' is the first definition.
(I know that snap is a class)
'children's game' is the second definition.
(children's card game)
'in' acts as a link.
(Other definitions for snap that I've seen before include "Break off - card-game" , "Picture" , "Bite at or utter angry words" , "Break sharply like dry twig" , "Speak irritably; photo" .)