Match ending in magnificent victory (4)
I believe the answer is:
twin
'match' is the definition.
(twinning is a kind of matching)
'ending in magnificent victory' is the wordplay.
'ending in' suggests the final letters.
'victory' becomes 'win' (I've seen this before).
The final letter of 'magnificent' is 't'.
't'+'win'='TWIN'
(Other definitions for twin that I've seen before include "One of two born together" , "Duplicate copy" , "One hotel room" , "Castor or Pollux?" , "Romulus or Remus" .)