Hands up for trade (4)
I believe the answer is:
swap
'trade' is the definition.
('swap' can be a synonym of 'trade')
'hands up' is the wordplay.
'hands' becomes 'paws' ('paw' can be a synonym of 'hand').
'up' is a reversal indicator (in down clue: letters go upwards).
'paws' back-to-front is 'SWAP'.
'for' acts as a link.
(Other definitions for swap that I've seen before include "Wasp (anag)" , "Interchange" , "exchanged gift" , "Exchange goods" , "Exchange, barter" .)