Freight vehicle on journey (5)
I believe the answer is:
cargo
'freight' is the definition.
(synonyms)
'vehicle on journey' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'on journey' becomes 'go' (I've seen this in other clues).
'car'+'go'='CARGO'
(Other definitions for cargo that I've seen before include "Ship's freight" , "Payload" , "Ship's load" , "Load carried" , "Goods carried by a large vehicle" .)