Fictional extraterrestrial mutant of a type created by Terry Nation in a 1963 Doctor Who serial (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
dalek
(Other definitions for dalek that I've seen before include "Alien creature" , "Alien creation" , "Croaky-voiced exterminator" , "mechanical creature" , "Hostile alien" .)