Game for trial marriage (4,5)
I believe the answer is:
test match
'game' is the definition.
(type of cricket game)
'trial marriage' is the wordplay.
'trial' becomes 'test' (synonyms).
'marriage' becomes 'match' (I've seen this before).
'test'+'match'='TEST MATCH'
'for' acts as a link.
(Other definitions for test match that I've seen before include "Ashes tie, perhaps" , "Sort of game" , "International meeting" , "Lord's international?" , "International fixture" .)