The argument against, try to dispute (7)
I believe the answer is:
contest
'dispute' is the definition.
(I've seen this in another clue)
'the argument against try' is the wordplay.
'the argument against' becomes 'con' (as in pros and cons).
'try' becomes 'test' (synonyms).
'con'+'test'='CONTEST'
'to' is the link.
(Other definitions for contest that I've seen before include "Tournament" , "Competition or conflict" , "Match" , "Competition; dispute" , "Oppose - competition" .)