The fun of Clash of Clans is sticking with your village through the good times and the bad times, so the game wasn't designed for being reset and restarted at a whim.
On iOS, you can only start a new village on a new device, but remember that your original villages stays connected to your Game Center account, and this can't be switched. On Android, you need to reinstall the application, but your previous village will remain permanently attached to your Google Play account (if you used Google Play Sign-In).