Defeated finally over issue? Resign (5)
I believe the answer is:
demit
'resign' is the definition.
(demit means to resign from a post)
'defeated finally over issue?' is the wordplay.
'finally' says to take the final letters.
'over' is a charade indicator (letters next to each other).
'issue?' becomes 'emit' (both can mean to give out or radiate).
The final letter of 'defeated' is 'd'.
'd'+'emit'='DEMIT'
(Other definitions for demit that I've seen before include "Timed (anag.); to lower or to resign" , "Send" , "Yield" , "Dismiss" .)