Home of the Ephesians (5)
I believe the answer is:
'home of the ephesians' 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 region of Eastern Mediterranean" , "Old region in Asia Minor" , "Aegean region which gives its name to the adjacent sea" , "Ancient Greek region" , "Ancient area" .)