In this building, are those inside waiting to buy it? (5,3)
I believe the answer is:
death row
'in this building are those inside waiting to buy it?' is the definition.
The definition suggests a singular noun which matches the answer.
This is all the clue.
(Other definitions for death row that I've seen before include "Cell block where prisoners await execution" , "Part of US prison for condemned murderers" , "special facility for condemned prisoners" , "In USA, part of prison where condemned criminals are held" , "Place for prisoners awaiting execution" .)