Photographer first cleans muddied glass, covering it with this (4,3)
I believe the answer is:
lens cap
'glass covering it with this' is the definition.
The definition suggests a singular noun which matches the answer.
'photographer first cleans muddied' is the wordplay.
'photographer first' becomes 'p' (1st letter of 'photographer').
'muddied' indicates anagramming the letters (I've seen 'muddy' mean this (letters get muddied or confused)).
'p'+'cleans'='pcleans'
'pcleans' anagrammed gives 'LENS CAP'.
Can you help me to learn more?
(Other definitions for lens cap that I've seen before include "protection for photographer" , "Aperture protector" , "Camera cover" .)