Building proposition at school (8)
I believe the answer is:
premises
'building' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'proposition at school' is the wordplay.
'proposition' becomes 'premise' (premise is a kind of proposition).
'at school' becomes 's' (I can't explain this - if you can you should believe this answer much more).
'premise'+'s'='PREMISES'
Can you help me to learn more?
(Other definitions for premises that I've seen before include "Buildings occupied by businesses" , "Places of business" , "Building, place of business" , "States" , "Property" .)