Wits needed for children's game (7)
I believe the answer is:
marbles
I believe this clue is a double definition.
'wits' is the first definition.
(marbles can informally mean wits or sanity)
'for children's game' is the second definition.
(I've seen this before)
'needed' is the link.
(Other definitions for marbles that I've seen before include "Glass balls to play with" , "Small spheres of glass - statuary" , "Game with alleys and taws" , "Sculptures" , "alleys, perhaps" .)