Slip out of the building (4)
I believe the answer is:
shed
This clue is a double definition.
'slip' is the first definition.
(thesaurus)
'the building' is the second definition.
(shed is a kind of building)
'out of' is the link.
(Other definitions for shed that I've seen before include "Outhouse -- cast" , "Garden store" , "Removed in garden hut" , "shelter" , "Garden feature" .)