Uneven railways removed, sadly (4)
I believe the answer is:
alas
'sadly' is the definition.
('alas' is used to express regret)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for alas that I've seen before include "Exclamation of misfortune" , "Antipodean island state" , "Lackaday" , "Woeful expression" , "By bad luck" .)