Will I lose my levels by clearing data?

Warm welcome!

If you backed up your progress through a King account or a Facebook account, you won't lose it if you've been online. Delete data means that all data, including boosters, will be deleted. So you're going to lose all the boosters. They are stored only on the device where they were obtained. 

After you deleted your data, your in-game login was also deleted. You'll need to log in again to see your progress and current level.

I hope I understood your question correctly and my answer helps.