Proverbially busy flier (3)

I believe the answer is:

bee

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

'proverbially busy flier' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

This is all the clue.

Can you help me to learn more?

(Other definitions for bee that I've seen before include "Social worker possibly" , "Hairy-bodied insect" , "Stinging insect" , "competition" , "Social insect" .)

I've seen this clue in The Mirror.

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.