Some TikTok viewers now have a less crowded viewing experience

If you enable Clear Mode, you will be able to view a TikTok video without all of the window chrome, but if you scroll to the next video, the UI will return, and you will need to reenable clear mode to receive the genuine full-screen video experience. That’s not how I’d expect it to work, but it makes sense for the company to develop the feature in this manner; it ensures that you’ll be able to see who made the video and what sound it uses.