Concede defeat (4,4)
I believe the answer is:
back down
'concede defeat' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for back down that I've seen before include "Withdraw challenge" , "Withdraw argument in face of opposition" , "Withdraw (aggressive) claim" , "Withdraw opinion or claim" , "Give up claim or withdraw argument" .)