Section of a train (3)
(Other definitions for car that I've seen before include "Auto" , "Hatchback, say?" , "Motor vehicle" , "One for the road?" , "Private vehicle" .)
'section of a train' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for carriage that I've seen before include "Bodily posture or wheeled vehicle" , "Section of a train" , "Transportation" , "Old form of transport, or body posture while walking" , "Buggy" .)