Hit with the palm (4)
I believe the answer is:
slap
'hit with the palm' 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 "Blow (in face, on back, wrist)" , "Blow, maybe in the face" , "Hit with the palm" , "Hit with a flat hand" , "Strike action" .)