Do business in wood? (4)
I believe the answer is:
deal
I believe this is a double definition.
'do business' is the first definition.
(as in doing a business deal)
'wood?' is the second definition.
(deal is a kind of wood)
'in' is the link.
(Other definitions for deal that I've seen before include "Soft wood or slang bargain" , "Agreement; soft wood" , "Give out (cards)" , "Distribute playing cards" , "split deck" .)