Light vehicle (4)
I believe the answer is:
cart
'light vehicle' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for cart that I've seen before include "Open wagon (to come after, not before, the horse)" , "Something not to be put in front of the horse" , "Old two-wheeled goods vehicle" , "Carrying vehicle" , "Primitive transport" .)