Keep a/the lid on something

1. To keep something secret. passer sous silence

• It's supposed to be a surprise, so try to keep a lid on it, will you?

2. to control the level of something in order to stop it increasing, to maintain control over something.- garder sous controle 

• His forces kept a lid on unrest for nearly eight years.
• Economic difficulties continued and the government intervened to keep a lid on inflation.