have first call on (something)

1. To have the rights to something. Hey, let your little brother have first call on riding shotgun in the car for once. Hey, I had first call on leading the line! A: "Can I have the last pudding cup?" B: "No, Sarah has first call on it."

2. To take top priority in a particular situation. This is a huge case for our firm, so it has first call on my time right now. Now that you're a married man, your family has got to have first call on your time. Well, if your health never has first call on your mind, no wonder you're always sick!

have first ˈcall (on somebody/something)

be the most important person or thing competing for somebody’s time, money, etc. and be dealt with or paid for before other people or things: The children always have first call on her time.