Cheers good children’s game (3)
I believe the answer is:
tag
'children's game' is the definition.
(playground game)
'cheers good' is the wordplay.
'cheers' becomes 'ta' (both can informally mean thank you).
'good' becomes 'g' (abbreviation).
'ta'+'g'='TAG'
(Other definitions for tag that I've seen before include "day in Berlin" , "Children's chasing game" , "Earmark" , "Label - children's game" , "Label or sticker" .)