Cess on one car (for hire) (4)
I believe the answer is:
taxi
'car for hire' is the definition.
(I've seen this before)
'cess on one' is the wordplay.
'cess on' becomes 'tax' (I am not sure about this - if you are sure you should believe this answer much more).
'one' becomes 'i' (Roman numeral).
'tax'+'i'='TAXI'
Can you help me to learn more?
(Other definitions for taxi that I've seen before include "Motor-cab" , "Hired vehicle" , "Motor cab" , "move slowly along the ground" , "Hackney carriage" .)