The documents are only available to people with 'security clearance' [=special permission given only to people who are approved to know or see secret things] from the government.
The car has a 'road/ground clearance' of seven inches. [=the bottom of the car is seven inches above the road/ground]
You'll have to get 'clearance' [='approval'] from management to go ahead with the project.
(..) - Tell me what I'm doing. - I'm not taking you to Montana. It's all I can do to keep it from turning into a tourist site for everybody who has a T.S. clearance. I'm just telling you what it would take to do this job. This is not a negotiation. If I leave here, your chance is gone. Good day. (..)2016 Arrival
(..) of everyone's list when it comes to translations. And you have another two years in the SSBI, so you still have top secret clearance. That's why I'm in your office and not in Berkeley. OK? I have something I need you to translate for me. (..)2016 Arrival