go up to bat

1. In baseball, to go to home plate and try to hit the ball. Lucy, you're going up to bat first, which means Mindy is on deck. No one was expecting a bunt when their star hitter went up to bat. When you go up to bat, don't swing at any pitches out of the strike zone, OK?

2. By extension, to present oneself in order to do or attempt something. You can go up to bat first and get the meeting started. Don't worry, we have some time—there are other speakers before we have to go up to bat. We were all nervous about our oral exam, so we drew numbers to determine who would go up to bat first.

3. By extension, to act in support (of someone). Usually followed by "for someone." Since you know the recruiter, do you think you can go up to bat for me? I really need this job. Thankfully, my manager went up to bat for me when the company was looking to lay off employees. Of course I'll go up to bat for you with the headmaster—I know you had nothing to do with this prank.