Old postman living abroad (5)
I believe the answer is:
expat
'living abroad' is the definition.
(I've seen this before)
'old postman' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'postman' becomes 'pat' (children's TV character Postman Pat).
'ex'+'pat'='EXPAT'
(Other definitions for expat that I've seen before include "Emigre" , "who now uses overseas address?" , "overseas settler" , "One who lives abroad" , "one settled abroad" .)