Dispute with jailbird before trial (7)
I believe the answer is:
contest
'dispute' is the definition.
(I know that dispute is a more specific form of the action contest)
'jailbird before trial' is the wordplay.
'jailbird' becomes 'con' (convict).
'before' means one lot of letters go next to another.
'trial' becomes 'test' (synonyms).
'con'+'test'='CONTEST'
'with' is the link.
(Other definitions for contest that I've seen before include "Oppose - competition" , "Tournament" , "Match" , "Competition or conflict" , "Competition; dispute" .)