Excise duty on one vehicle (4)
I believe the answer is:
taxi
'vehicle' is the definition.
(I know that taxi is a type of motor car)
'excise duty on one' is the wordplay.
I cannot really see how this works, but
'excise' could be 'tax' (I've seen this in another clue) and 'tax' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for taxi that I've seen before include "I hail you!" , "Prepare to fly" , "use apron" , "Rank occupant" , "run along the ground" .)