Transport for vagrant mostly (4)
I believe the answer is:
tram
'transport' is the definition.
(tram is a kind of transport)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for tram that I've seen before include "Bus on rails" , "An early form of Luas in Dublin transport" , "Vehicle running on rails in road" , "Car on rails" , "Electrically driven transport" .)