Sailor facing route overseas (6)
I believe the answer is:
abroad
'overseas' is the definition.
(synonyms)
'sailor facing route' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'facing' says to put letters next to each other.
'route' becomes 'road' (synonyms).
'ab'+'road'='ABROAD'
(Other definitions for abroad that I've seen before include "In foreign land" , "Stare lecherously at (someone)" , "over a wide area" , "In a foreign country" , "out of UK?" .)