Smart game to play outside (6)
I believe the answer is:
snappy
'smart' is the definition.
(I've seen this before)
'game to play outside' is the wordplay.
'game' becomes 'snap' (card game).
'to' says to put letters next to each other.
'outside' suggests removing the centre.
'play' with its middle removed is 'py'.
'snap'+'py'='SNAPPY'
(Other definitions for snappy that I've seen before include "Ratty" , "Cleverly concise; stylish" , "Irritable - quick - fashionable" , "Smart - lively" , "Quick and energetic" .)