Disparage in notes to the railway (5)
I believe the answer is:
decry
'disparage' is the definition.
(I've seen this in another clue)
'notes to the railway' is the wordplay.
'notes' becomes 'de' (two musical notes).
'to the railway' becomes 'cry' (I can't justify this - if you can you should believe this answer much more).
'de'+'cry'='DECRY'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for decry that I've seen before include "Run down" , "Speak of in slighting way, belittle" , "Disparage, put down" , "Disapprove of" , "'Condemn, belittle (5)'" .)