Two sailors coming to unknown region of old (7)
I believe the answer is:
tartary
'region of old' is the definition.
(historical name for a region of Asia)
'two sailors coming to unknown' is the wordplay.
'two sailors' means two substitutions for 'sailor'.
'sailor' becomes 'tar' (slang term for a sailor).
'sailor' becomes 'tar' (slang term for a sailor).
'coming to' is a charade indicator (letters next to each other).
'unknown' becomes 'y' (algebra).
'tar'+'tar'+'y'='TARTARY'
(Other definitions for tartary that I've seen before include "historical region long ago" , "central Eurasian area" .)