Ancient Aegean Sea region (5)
I believe the answer is:
ionia
'ancient aegean sea region' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ionia that I've seen before include "Ancient Greek colony" , "ancient region of Eastern Mediterranean" , "Old region in Asia Minor" , "where Greeks settled" , "East coast of the Aegean in Classical times" .)