be on

verb4

1. •
   To be responsible for (something).

   • That task is on you.
2. •
   To be up to; to be engaged in or scheduled to do imminently.

   • What are you on today?
3. •
   (UK) To be ranked at (something), based on polling.

   • The Tories are on twenty-five percent in that constituency.
4. •
   To be performative or funny in a wearying manner.

   • You don't have to be on all the time.