Bygone sovereign
I believe the answer is:
shah
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bygone sovereign</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for shah that I've seen before include "Former Persian title" , "Old king" , "Former Iranian monarch" , "Persian king" , "Old Middle Eastern ruler" .)