in on it—(also: in at it) taking part in an activity; involved in smth.:
- We’re sure of one thing—it wasn’t a one-man job. But were there two, three, or four of them in on it?
on it—
1. (U.S. sl.) well able to do smth.; in control of a situation or a task:
- You bet he could cook. He was just on it.
2. (Austral. sl.) drinking heavily:
- When he was on it, and wanted another drink … he never had to press the bell, but pressed the button with a bullet.