The "Clear clipboard" setting clears single-item clipboards by copying a blank value, " ", to the clipboard. Multi-item clipboards, such as Samsung's, prove more difficult as they can store copied values beyond where 1Password can clear them. Some devices also have a clipboard manager running in the background which can retain copied values separately. While it may not work with every device or clipboard manager, we're currently working on some changes to be able to clear the clipboard in as many places as we can.