Truck left gold by railway (5)
I believe the answer is:
lorry
'truck' is the definition.
(I know that truck can be written as lorry)
'left gold by railway' is the wordplay.
'left' becomes 'l' (common abbreviation).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'by' means one lot of letters go next to another.
'railway' becomes 'ry' (abbreviation for railway).
'l'+'or'+'ry'='LORRY'
(Other definitions for lorry that I've seen before include "Large truck" , "Load-carrying vehicle" , "Large motor vehicle for transporting goods" , "From which stolen goods fall?" , "Industrial vehicle" .)