Hit with an open hand (4)
I believe the answer is:
slap
'hit with an open hand' 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 "Mild punishment" , "Right" , "Strike (in the face)" , "Blow, maybe in the face" , "Blow (in face, on back, wrist)" .)