Travel by railway? It’s bloody! (4)
I believe the answer is:
gory
'bloody' is the definition.
(similar in meaning)
'travel by railway?' is the wordplay.
'travel' becomes 'go' (synonyms).
'by' says to put letters next to each other.
'railway?' becomes 'ry' (abbreviation for railway).
'go'+'ry'='GORY'
'it's' acts as a link.
(Other definitions for gory that I've seen before include "Grisly" , "Maybe gruesome" , "Involving much bloodshed" , "Horrific" , "Bloodstained" .)