Notice it’s exclusive! (4,3)

I believe the answer is:

keep out

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

'notice' is the definition.
Although both the answer and definition are verbs in their base form, I can't understand how they can define each other.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for keep out that I've seen before include "Exclude" , "warning note to trespassers?" , "No entry!" , "Private land sign" , "notice to trespassers?" .)

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.