Protect a railway employee (5)
I believe the answer is:
guard
I believe this clue is a double definition.
'protect' is the first definition.
(I know that guard is a kind of protect)
'a railway employee' is the second definition.
(I know that guard is a type of railway worker)
(Other definitions for guard that I've seen before include "Custodian" , "Protect(or)" , "Police" , "Sentry" , "Screw" .)