first order of the day

noun2

1. •
   An item of business that will be discussed before any other item on a particular day when a legislature is sitting.

   • ...from the Commons should be the first Order of the day. — 1699
2. •
   A goal or task that is of primary importance and will or should be pursued before any other goal.

   • There are two things every union member should make the first order of the day the pay envelope comes around — supply his family and pay his union dues. — 1921