Trade board (4)
I believe the answer is:
deal
This clue is a double definition.
'trade' is the first definition.
('deal' can be a synonym of 'trade')
'board' is the second definition.
(deal is a kind of board)
(Other definitions for deal that I've seen before include "split deck" , "Plank of softwood timber" , "Wood - piece of business" , "Sawn wood" , "Share out (cards); wood" .)