Sacred building, outstanding (8)
I believe the answer is:
hallowed
'sacred' is the definition.
('hallowed' can be similar in meaning to 'sacred')
'building outstanding' is the wordplay.
'building' becomes 'hall' (hall is a kind of building).
'outstanding' becomes 'owed' ('owed' can be a synonym of 'outstanding').
'hall'+'owed'='HALLOWED'
(Other definitions for hallowed that I've seen before include "Respected" , "Reverenced" , "sacrosanct" , "Made blessed" , "Made holy and honoured" .)