Keeping mum and keeping oneself warm (8,2)

I believe the answer is:

wrapping up

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

'keeping' is the definition.
Although both the answer and definition are present participle verbs, I don't understand how one could define the other.

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

Can you help me to learn more?

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.