Carbon works in Barrow (4)
I believe the answer is:
cart
'barrow' is the definition.
(thesaurus)
'carbon works' is the wordplay.
'carbon' becomes 'C' (C is the chemical symbol for carbon).
'works' becomes 'art' (I've seen this before).
'c'+'art'='CART'
'in' acts as a link.
(Other definitions for cart that I've seen before include "Farm vehicle" , "Two-wheeled, drawn vehicle" , "Don't put this before the horse (4)" , "Hump" , "Light vehicle" .)