Low cart (4)
'low cart' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dray that I've seen before include "Brewery wagon" , "Squirrel's home" , "Strong low cart for heavy loads" , "Cart without sides, for delivering barrels" , "Low truck" .)
(Other definitions for trolley that I've seen before include "Basket, truck on wheels" , "Shopping vehicle" , "American tram or supermarket purchases carrier" , "Supermarket vehicle" , "tramcar" .)