Old Irishman living abroad! (5)
I believe the answer is:
expat
'living abroad' is the definition.
(I've seen this before)
'old irishman' is the wordplay.
'old' becomes 'ex'.
'irishman' becomes 'pat'.
'ex'+'pat'='EXPAT'
(Other definitions for expat that I've seen before include "Emigre" , "One living abroad (abbrev.)" , "overseas settler" , "Brit abroad, say" , "he has emigrated" .)