Country on the Caspian Sea (4)
I believe the answer is:
iran
'country on the caspian sea' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for iran that I've seen before include "Former Persia" , "Tehran is its capital" , "Country lying to south of Caspian sea" , "Previously known as Persia" , "Middle East country" .)