A lot or a little?
Parents need to know that Clubhouse: Drop-in audio chat is a voice-only chat-based app. At the time of review, new users need to receive an invite from a current user or join a waitlist. There are quite a few celebrities using the app, which will likely draw younger users, and there are sometimes big names like Elon Musk who attract lots of listeners. Users can drop in and out of "rooms" that are usually focused on a particular topic without drawing attention to themselves. There are moderators who can mute and remove people from a group. However, because the app is intended for adults, the conversations are often very mature, including sexually explicit language, all manner of swearing, and discussion of substance use. Profile pictures also sometimes feature scantily clad people. The adult-focused content can also be also tame, like the rooms about networking or growing a business. Users can start rooms and lock them so random users can't drop in.
The terms of service state that users should be 18 or older to use the app. While the ability to join a private room and some of the topics could be a supportive or informative outlet for younger teens, their use of the app would require lots of parental involvement. Also, there are many rooms and clubs moderated by people of color and people in the LGBTQ+ community, which provide a space that many social media platforms lack. Many users include their Twitter and Instagram handles in their profiles, which they use to send direct messages since that functionality doesn't exist in the app at the time of review. Though you can refuse, the app requests access to your contacts. Read the developer's privacy policy for details on how your (or your kids') information is collected, used, and shared and any choices you may have in the matter, and note that privacy policies and terms of service frequently change.