Bar means of transport (4)
I believe the answer is:
rail
I believe this clue is a double definition.
'bar' is the first definition.
(I know that rail is a type of bar)
'means of transport' is the second definition.
(I've seen this in another clue)
(Other definitions for rail that I've seen before include "Track - complain - bird" , "method of transport" , "Track for wheels" , "Bar for hanging; bird as corncrake" , "Barrier around lair" .)