Duel provoker (4)
I believe the answer is:
slap
'duel provoker' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slap that I've seen before include "Right" , "Strike with the palm" , "Hit with an open hand" , "Blow, maybe in the face" , "Hit with the palm" .)