Tap the Info icon inside the Circle to open the Circle Info screen. Tap the Leave Circle button. Leaving a Circle will remove all your contributions (photos, videos, comments, and reactions).
PhotoCircle for Business Users
Business Platform users can leave/inactivate their organization circles without removing their contributions to those circles. This frees up their "workspace" in the app. User can rejoin/activate the circle later on by tapping the + button on the main screen and then tapping Join Group Circle to load the list of circles available to them.