A person, alternatively a house (5)
I believe the answer is:
manor
'a house' is the definition.
(manor is a kind of house)
'a person alternatively' is the wordplay.
'a person' becomes 'man' (man is a kind of person).
'alternatively' becomes 'or'.
'man'+'or'='MANOR'
(Other definitions for manor that I've seen before include "local copper's area" , "Grand but strange Roman house" , "Landed estate" , "Country seat" , "Mansion of a wealthy person" .)