Partner after ton in match (5)
I believe the answer is:
tally
'match' is the definition.
('tally' can be a synonym of 'match')
'partner after ton' is the wordplay.
'partner' becomes 'ally' (I've seen this in other clues).
'after' is a charade indicator (letters next to each other).
'ton' becomes 't'.
'ally' put after 't' is 'TALLY'.
'in' acts as a link.
(Other definitions for tally that I've seen before include "Coincide" , "Mark" , "Agree, add up" , "Reckoning of a debt or of votes" , "highly?" .)