Train bar? (4)
I believe the answer is:
rail
I believe this clue is a double definition.
'train' is the first definition.
(I know that train can be written as rail)
'bar?' is the second definition.
(I know that rail is a type of bar)
(Other definitions for rail that I've seen before include "Bar; waterbird" , "Horizontal bar - bird - complain" , "Bar of track or fence" , "Barrier around lair" , "Complain bitterly - wading bird" .)