Sailor on the way overseas (6)
I believe the answer is:
abroad
'overseas' is the definition.
(synonyms)
'sailor on the way' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'the way' becomes 'road' (road is a kind of way).
'ab'+'road'='ABROAD'
(Other definitions for abroad that I've seen before include "out of UK?" , "in the field" , "over a wide area" , "Pole would be so" , "In another country, not at home" .)