Charge one type of vehicle (4)
I believe the answer is:
taxi
'type of vehicle' is the definition.
(I've seen this before)
'charge one' is the wordplay.
'charge' becomes 'tax' (tax is a kind of charge).
'one' becomes 'i' (Roman numeral).
'tax'+'i'='TAXI'
(Other definitions for taxi that I've seen before include "At airport, guide" , "move on ground before take-off" , "Move along a runway" , "Minicab" , "Motor vehicle by rank?" .)