A game involving more of us (8)
I believe the answer is:
foursome
'a game' is the definition.
(thesaurus)
'involving more of us' is the wordplay.
'involving' indicates anagramming the letters.
'more'+'of'+'us'='moreofus'
'moreofus' with letters rearranged gives 'FOURSOME'.
(Other definitions for foursome that I've seen before include "enough for rubber" , "Quartet" , "The Beatles, for example" , "golf match" , "In game" .)