Villainous knight brings extra fear, we hear (7)

I believe the answer is:

mordred

I'm a little stuck... Click here to teach me more about this clue!

'villainous knight' is the definition.
'mordred' can be an answer for 'knight' (I've seen this before). I'm not certain of the 'villainous' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for mordred that I've seen before include "King Arthur's nephew, who abducted Guinevere" , "knight" .)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.