It doesn’t make for good viewing (3)
I believe the answer is:
fog
'it doesn't make for good viewing' is the definition.
The definition suggests a singular noun which matches the answer.
This is the entire clue.
Can you help me to learn more?
(Other definitions for fog that I've seen before include "Confusion" , "Bank restricting visibility" , "Miasma" , "Impenetrable mist" , "second growth of grass" .)