Despotic ruler (6)
I believe the answer is:
tyrant
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">despotic ruler</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 tyrant that I've seen before include "taskmaster" , "Authoritarian" , "Arbitrary ruler" , "Oppressive and cruel ruler" , "Harsh and absolute ruler" .)