Hold contents of vehicle on journey (5)
I believe the answer is:
cargo
'hold contents' is the definition.
(I've seen this before)
'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'
'of' acts as a link.
(Other definitions for cargo that I've seen before include "Freight, load" , "Baggage" , "Freight on board ship" , "stuff to be carried by ship" , "Stuff on board" .)