Try line covered in blood (4)
I believe the answer is:
gory
'covered in blood' is the definition.
(I've seen this before)
'try line' is the wordplay.
'try' becomes 'go' (both can mean an attempt).
'line' becomes 'ry' (abbreviation for railway).
'go'+'ry'='GORY'
(Other definitions for gory that I've seen before include "Involving much bloodshed" , "Steeped in blood" , "Horrific" , "Violent; bloody" , "Maybe gruesome" .)