first port of call

noun

The library is often the first port of call for students looking for research materials.

意味（1）

(nautical) The first port that a vessel calls in at after the start of a voyage

After leaving from Southampton, our first port of call will be Gibraltar.

意味（2）

(idiomatic) The first place to go to start a process.

When you move to a new country, your first port of call is often the local police.