Monarch leaving count stupefied (4)

I believe the answer is:

numb

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

'stupefied' is the definition.
(I've seen this in another clue)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for numb that I've seen before include "Anaesthetised, unfeeling" , "Feeling nothing" , "Lacking sensation" , "Dead" , "Without sensation" .)

I've seen this clue in The Sun.

Want a hint initially instead of a full solution? Install my app