You don't need TSA PreCheck if you have Clear, but you should know that having Clear alone only exempts you from the first part of the TSA security screening process, which is checking your boarding pass and ID. To save time and hassle at the physical security screening, you would need TSA PreCheck.

CLEAR+ does not allow you to skip the TSA security screening entirely, but it does allow you to bypass the standard document check line. When you use CLEAR, you go to a dedicated kiosk where your identity is verified using biometrics (fingerprints or iris scans) instead of showing a physical ID to a TSA agent. After verification, a CLEAR ambassador escorts you directly to the front of the security screening area. If you also have TSA PreCheck®, you are taken to the front of the PreCheck lane, where you can keep your shoes and light jacket on and leave electronics in your bag. If you do not have PreCheck, you are taken to the front of the standard line where you must follow all regular screening procedures. Essentially, CLEAR handles the "identity" portion of security, while the TSA still handles the "physical" screening of your person and belongings.