Transport vehicle on railway (5)
I believe the answer is:
carry
'transport' is the definition.
('carry' can be a synonym of 'transport')
'vehicle on railway' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'on' is a charade indicator (letters next to each other).
'railway' becomes 'ry' (abbreviation for railway).
'car'+'ry'='CARRY'
(Other definitions for carry that I've seen before include "Have on one's person" , "Transport; bear" , "Be pregnant (with)" , "Convey, tote" , "Transport, fetch" .)