How to accuse a person suspected of arson? (5)

I believe the answer is:

hotly

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

'how' is the definition.
Both the answer and definition are adverbs. Maybe there's an association between them I don't understand?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for hotly that I've seen before include "With zeal - as one may be pursued" , "showing passion" , "disputed thus?" , "showing eagerness" , "Heatedly" .)

I've seen this clue in the Evening Standard.

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.