Railway company carries one for ship (5)
I believe the answer is:
liner
'one for ship' is the definition.
(as in an ocean liner)
'railway company carries' is the wordplay.
'railway' becomes 'line' (line is a kind of railway).
'company carries' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'line'+'r'='LINER'
Can you help me to learn more?
(Other definitions for liner that I've seen before include "Material applied to inner surface" , "that's put in bin" , "Seagoing vessel - goes with bin, eye or hard" , "Pleasure cruiser" , "Large ship or removable layer of material" .)