Royal domain (5)
I believe the answer is:
realm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">royal domain</span>' is the definition.<br/ ><span class="explanation-format__explanation">(realm can mean a kingdom)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for realm that I've seen before include "World" , "Area of influence" , "region" , "Monarchy" , "Area of interest/activity" .)