Foe of Doctor Who (5)
I believe the answer is:
dalek
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">foe of doctor who</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 dalek that I've seen before include "Doctor Who creature" , "Croaky-voiced exterminator" , "Alien enemy" , "Alien creation" , "Foe of Dr Who" .)