A sultanate (4)
I believe the answer is:
oman
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a sultanate</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for oman that I've seen before include "monarchy" , "Muscat's country" , "Arabian peninsula country" , "Sultanate, capital Muscat" , "Sultanate on the south-east coast of the Arabian Peninsula" .)