Drunkard eating cheese unknown? Not what he’s known for (8)
I believe the answer is:
sobriety
'not what he's known for' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'drunkard eating cheese unknown?' is the wordplay.
'drunkard' becomes 'sot' (synonyms).
'eating' indicates putting letters inside.
'cheese' becomes 'brie' (Brie is an example).
'unknown?' becomes 'y' (algebra).
'sot' enclosing 'brie' is 'sobriet'.
'sobriet'+'y'='SOBRIETY'
Can you help me to learn more?
(Other definitions for sobriety that I've seen before include "characteristic of judge, supposedly" , "Calmness, gravity" , "Calmness, dispassion" , "Serious and self-controlled state, no booze" , "Opposite of drunkenness" .)