The vehicle I sent off in a container (8)
I believe the answer is:
canister
'a container' is the definition.
(canister is a kind of container)
'the vehicle i sent off in' is the wordplay.
'the vehicle' becomes 'car' (car is a kind of vehicle).
'off' indicates an anagram.
'in' means one lot of letters goes inside another.
'i'+'sent'='isent'
'isent' anagrammed gives 'niste'.
'car' placed around 'niste' is 'CANISTER'.
(Other definitions for canister that I've seen before include "Metal container, for tea say" , "Vessel" , "Metal case" , "Metal food container" , "Tea-caddy" .)