Monarch's domain (5)
I believe the answer is:
realm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">monarch's domain</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for realm that I've seen before include "Province" , "Dominion" , "Country" , "department" , "Kingdom or sphere" .)