Old sailor housed by New York official (6)
I believe the answer is:
notary
'official' is the definition.
(notary is a kind of official)
'old sailor housed by new york' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'sailor' becomes 'tar' (tar is a kind of sailor).
'housed by' is an insertion indicator.
'new york' becomes 'ny'.
'o'+'tar'='otar'
'otar' put into 'ny' is 'NOTARY'.
(Other definitions for notary that I've seen before include "Official legally authorised to witness signatures" , "One legally empowered to witness signatures and certify documents" , "One authorised to certify legal documents" , "Person legally empowered to witness signatures" , "Solicitor authorised to administer oaths and certify documents" .)