Moved app icon reappears in original location

Suddenly, the clock app icon showed up in the favorites tray on our Moto g phone. There already is a clock app icon on the home screen, which means there are now TWO clock icons on the screen. I don't want it in the favorites tray. I tried to remove the tray clock icon by pressing on it and dragging it to the screen top to remove it but the remove box doesn't appear and the icon I'm dragging falls back to the screen -- which means I now have THREE clock icons on the screen. How do I remove the tray clock icon permanently? Thanks.