settle down phrasal verb ( see also ↑ settle )
1 . settle (somebody) down to become quiet and calm, or to make someone quiet and calm:
Shh! Settle down, please! Now turn to page 57.
When Kyle was a baby, we used to take him for rides in the car to settle him down.
2 . to start living a quiet and calm life in one place, especially when you get married:
They’d like to see their daughter settle down, get married, and have kids.
3 . to start giving all of your attention to a job or activity
settle down to
I sorted out my mail, then settled down to some serious work.
4 . if a situation settles down, it becomes calmer and you are less busy or less worried:
It’s been really hectic here. When things settle down, I’ll give you a call.