Exclude new building (4)
I believe the answer is:
barn
'building' is the definition.
(barn is a kind of building)
'exclude new' is the wordplay.
'exclude' becomes 'bar' ('bar' can be a synonym of 'exclude').
'new' becomes 'n'.
'bar'+'n'='BARN'
(Other definitions for barn that I've seen before include "stable" , "Type of dance or owl" , "Large shed" , "Housing for farm animals" , "Farm store" .)