Nose and ears not a game (7)
I believe the answer is:
conkers
'nose and ears not a game' is the definition.
I can't tell whether this defines the answer.
'nose and ears not a' is the wordplay.
'nose' becomes 'conk' (informal term for nose).
'and' means one lot of letters go next to another.
'not' indicates named letters should be taken away.
'ears' with 'a' taken away is 'ers'.
'conk'+'ers'='CONKERS'
(Other definitions for conkers that I've seen before include "Schoolchildren's game" , "Children's game" , "Game using horse chestnuts" , "game with strikers" , "Horse chestnut seeds" .)