I am after a levy for transport (4)
I believe the answer is:
taxi
'for transport' is the definition.
(taxi is a kind of transport)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for taxi that I've seen before include "run along the ground" , "Car for hire" , "Part of fleet" , "Prepare to take off" , "Motor-cab" .)