Knock pals around (4)
I believe the answer is:
slap
'knock' is the definition.
(thesaurus)
'pals around' is the wordplay.
'around' says the letters should be written backwards.
'pals' written backwards gives 'SLAP'.
(Other definitions for slap that I've seen before include "Blow, maybe in the face" , "Right" , "A blow among pals" , "Hit with an open hand" , "Mild punishment" .)