Addition to a building (9)
I believe the answer is:
extension
(Other definitions for extension that I've seen before include "Annexe" , "Office phone, perhaps" , "supplement" , "telephone number" , "Another phone" .)
I believe the answer is:
extension
(Other definitions for extension that I've seen before include "Annexe" , "Office phone, perhaps" , "supplement" , "telephone number" , "Another phone" .)