It ought to be soundly curbed for safety (7)
I believe the answer is:
roadway
This could be a double definition.
'it ought' is the first definition.
The definition suggests a singular noun which matches the answer.
'soundly curbed for safety' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'to be' is the link.
Can you help me to learn more?
(Other definitions for roadway that I've seen before include "Part of street for traffic" , "Traffic surface" , "Thoroughfare" , "On which vehicles travel" , "Surface travelled over" .)