Cheese eaten by habitual drunkard unknown for temperance (8)
I believe the answer is:
sobriety
'temperance' is the definition.
(sobriety is a kind of temperance)
'cheese eaten by habitual drunkard unknown' is the wordplay.
'cheese' becomes 'brie' (Brie is an example).
'eaten by' indicates putting letters inside.
'habitual drunkard' becomes 'sot' (I've seen this before).
'unknown' becomes 'y' (algebra).
'brie' placed inside 'sot' is 'sobriet'.
'sobriet'+'y'='SOBRIETY'
'for' acts as a link.
(Other definitions for sobriety that I've seen before include "Abstinence" , "Temperance" , "Calmness -- 8 -- by Tories (anag)" , "Refraining from" , "Serious and self-controlled state, no booze" .)