Jack on the way overseas (6)
I believe the answer is:
abroad
'overseas' is the definition.
('abroad' can be a synonym of 'overseas')
'jack on the way' is the wordplay.
'jack' becomes 'ab'.
'on' is a charade indicator (letters next to each other).
'the way' becomes 'road' (road is a kind of way**).
'ab'+'road'='ABROAD'
(Other definitions for abroad that I've seen before include "on the Continent" , "Stare lecherously at (someone)" , "to France, maybe" , "not in Britain" , "In foreign land" .)