Load vehicle then depart (5)
I believe the answer is:
cargo
'load' is the definition.
(I know that load can be written as cargo)
'vehicle then depart' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'then' means one lot of letters go next to another.
'depart' becomes 'go' (synonyms).
'car'+'go'='CARGO'
(Other definitions for cargo that I've seen before include "Freight on board ship" , "Hold contents" , "Load carried" , "Freight, load" , "Ship's freight" .)