Ancient region on the Adriatic Sea including parts of present-day Albania, Croatia and Montenegro (7)
I believe the answer is:
illyria
(Other definitions for illyria that I've seen before include "Orsino's dukedom" , "Roman Adriatic province" , "Orsino's place" , "Ancient Adriatic region, scene of "Twelfth Night"" , "setting at start of Twelfth Night" .)