Greek sorceress, niece of Circe (5)
I believe the answer is:
medea
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">greek sorceress</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">niece of circe</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for medea that I've seen before include "Jason's sorceress" , "Tragedy by Euripedes" , "Play by Euripides" , "Sorceress involved with Jason" , "Mythical enchantress" .)