Enter game play, making contract (9)
I believe the answer is:
agreement
'contract' is the definition.
(thesaurus)
'enter game play' is the wordplay.
'play' is an anagram indicator.
'enter'+'game'='entergame'
'entergame' anagrammed gives 'AGREEMENT'.
'making' acts as a link.
(Other definitions for agreement that I've seen before include "deal" , "Union < matching" , "consensus" , "understanding" , "Pact" .)