He has an unsuccessful winter on the railway (5)
I believe the answer is:
terry
'he' is the definition.
'an unsuccessful winter on the railway' is the wordplay.
'an unsuccessful winter' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' is a charade indicator (letters next to each other).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'railway' becomes 'ry' (abbreviation for railway).
'er' after 't' is 'ter'.
'ter'+'ry'='TERRY'
'has' acts as a link.
Can you help me to learn more?
(Other definitions for terry that I've seen before include "Towelling material" , "Cloth to make towels" , "(Rhyming) man's name" , "Terence (dim.)" , "Loop of pile fabric; England footballer" .)