Disparage in notes to the railway (5)
I believe the answer is:
decry
'disparage' is the definition.
(I've seen this before)
'notes to the railway' is the wordplay.
'notes' becomes 'dec' (I can't explain this - if you can you should give a lot more credence to this answer).
'to the railway' becomes 'ry' (abbreviation for railway).
'dec'+'ry'='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)'" .)