Railwayman's uniform covered by pullover (5)
I believe the answer is:
guard
This clue could be a double definition.
'railwayman's' is the first definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'uniform covered by pullover' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
Can you help me to learn more?
(Other definitions for guard that I've seen before include "Yeomen" , "Sentry" , "Protect(or)" , "Protection" , "security man" .)