Each evening going on railway (5)
I believe the answer is:
every
'each' is the definition.
(synonyms)
'evening going on railway' is the wordplay.
'evening' becomes 'eve' (synonyms).
'going on' says to put letters next to each other.
'railway' becomes 'ry' (abbreviation for railway).
'eve'+'ry'='EVERY'
(Other definitions for every that I've seen before include "'God bless us - - one !'" , "Each (one of a set)" , "All possible; the utmost" , "The best possible" , "As much as possible" .)