It clouds one's vision of a road and a street (4)
I believe the answer is:
mist
'it clouds one's vision' is the definition.
The definition suggests a singular noun which matches the answer.
'road and a street' is the wordplay.
'road' becomes 'MI' (resembles M1 motorway).
'and' says to put letters next to each other.
'a street' becomes 'st' (abbreviation).
'mi'+'st'='MIST'
'of a' is the link.
Can you help me to learn more?
(Other definitions for mist that I've seen before include "Fret" , "low-level cloud" , "Mizzle; light rain" , "Slight fog" , "Cloud; thin fog" .)