Lift up cobber's clobber (4)
I believe the answer is:
slap
'clobber' is the definition.
'lift up cobber's' is the wordplay.
'lift up' is a reversal indicator.
'cobber's' becomes 'pals'.
'pals' backwards is 'SLAP'.
(Other definitions for slap that I've seen before include "Hit with an open hand" , "Strike with the palm" , "Blow, maybe in the face" , "Mild punishment" , "Strike (in the face)" .)