How good, but rather frightening, the story was? (8)

I believe the answer is:

rattling

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

But I can't explain it at all! Could you help me understand?

(Other definitions for rattling that I've seen before include "Quick and energetic" , "Noisily shaking (as in good yarn)" , "Extraordinarily good, for a snake?" , "Smart" , "worrying" .)

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.