Despicable person, endlessly uncivil (3)

I believe the answer is:

cur

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

'despicable person' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for cur that I've seen before include "Inferior dog or one of mixed breed" , "Aggressive dog" , "Worthless mongrel" , "Mangy dog" , "Mongrel - coward" .)

I've seen this clue in The Times.

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.