Hit friends turning up (4)
I believe the answer is:
slap
'hit' is the definition.
(thesaurus)
'friends turning up' is the wordplay.
'friends' becomes 'pals' (pal is a kind of friend).
'turning up' is a reversal indicator.
'pals' backwards is 'SLAP'.
(Other definitions for slap that I've seen before include "Hit with a flat hand" , "Right" , "Blow, maybe in the face" , "Cuff" , "Strike with the palm" .)