Switch hands back (4)
I believe the answer is:
swap
'switch' is the definition.
('swap' can be a synonym of 'switch')
'hands back' is the wordplay.
'hands' becomes 'paws' ('paw' can be a synonym of 'hand').
'back' shows that the letters should be reversed in order.
'paws' backwards is 'SWAP'.
(Other definitions for swap that I've seen before include "exchanged gift" , "Switch" , "Change over" , "Exchange for paws" , "exchanged item" .)