Overturn result after leading (5)
I believe the answer is:
upend
'overturn' is the definition.
(to upend is to turn over)
'result after leading' is the wordplay.
'result' becomes 'end' (I've seen this before).
'after' is a charade indicator (letters next to each other).
'leading' becomes 'up' (up can mean winning a sports match).
'end' after 'up' is 'UPEND'.
(Other definitions for upend that I've seen before include "Invert" , "Flip" , "Overturn" , "make stand" , "Affect drastically" .)