Overseas in Seaman Street (6)
I believe the answer is:
abroad
'overseas' is the definition.
(synonyms)
'seaman street' is the wordplay.
'seaman' becomes 'ab'.
'street' becomes 'road' (I've seen this before).
'ab'+'road'='ABROAD'
'in' acts as a link.
(Other definitions for abroad that I've seen before include "Away in another country" , "in France, say" , "Europe, for example" , "In another country, not at home" , "in Paris, perhaps" .)