Friends brought back smack (4)
I believe the answer is:
slap
'smack' is the definition.
('slap' can be a synonym of 'smack')
'friends brought back' is the wordplay.
'friends' becomes 'pals' (pal is a kind of friend).
'brought back' is a reversal indicator.
'pals' in reverse letter order is 'SLAP'.
(Other definitions for slap that I've seen before include "Blow (in face, on back, wrist)" , "Right" , "Make-up (slang)" , "Strike (in the face)" , "Hit with a flat hand" .)