Do break some in game (8)
I believe the answer is:
dominoes
'game' is the definition.
(dominoes is a kind of game)
'do break some in' is the wordplay.
'break' indicates anagramming the letters.
'some'+'in'='somein'
'somein' anagrammed gives 'minoes'.
'do'+'minoes'='DOMINOES'
(Other definitions for dominoes that I've seen before include "Mistakes" , "Traditional pub game" , "Game played with black pieces with white spots" , "masks" , "Game with twenty-eight pieces" .)