the act of doing or organizing something without the knowledge of someone; doing a trick, stunt, or prank.

Is setting up correct?

Setup is a noun that refers to an arrangement. Set up is a phrasal verb that refers to making preparations for something.

What does set up mean in slang?

a situation in which someone is tricked into doing something or is made to seem guilty of something they did not do: When drugs were found in her luggage, she claimed it was a set-up.