Vehicle in trading centre heading north (4)
I believe the answer is:
tram
'vehicle' is the definition.
(tram is a kind of vehicle)
'trading centre heading north' is the wordplay.
'trading centre' becomes 'mart' (I've seen this before).
'heading north' says the letters should be written backwards.
'mart' written backwards gives 'TRAM'.
'in' is the link.
(Other definitions for tram that I've seen before include "Passenger vehicle on rails" , "Former public vehicle" , "Vehicle running on rails in road" , "Take it to the mart" , "Road vehicle running on tracks" .)