Building's correct temperature unknown (8)
I believe the answer is:
property
'building's' is the definition.
(property can mean a building or residence)
'correct temperature unknown' is the wordplay.
'correct' becomes 'proper' (similar in meaning).
'temperature' becomes 't' (abbreviation).
'unknown' becomes 'y' (algebra).
'proper'+'t'+'y'='PROPERTY'
(Other definitions for property that I've seen before include "Buildings" , "Quality; building" , "Attribute; chattel" , "Belongings" , "Possessions; characteristic" .)