Monarch's rule (5)
I believe the answer is:
reign
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">monarch's rule</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 reign that I've seen before include "Sovereign's rule" , "Niger (anag)" , "Occupy the throne" , "period in power" , "Monarch's rule" .)