Sharp rebuke (4)
I believe the answer is:
slap
'sharp rebuke' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slap that I've seen before include "A blow among pals" , "Hit with the palm" , "Strike with the palm" , "Right" , "Blow (in face, on back, wrist)" .)