Open Clash Royale on your iPhone or iPad
Go to Settings in the game
Tap Supercell ID
Tap Log Out
Close the game completely
Open Settings on your iPhone or iPad
Tap Game Center
Turn off Game Center or sign out of the current Apple ID if needed
Open Clash Royale again
If prompted, choose to play without Supercell ID or start a new account
Complete the tutorial to create the new account
If you want to keep the new account, connect it to a new Supercell ID
If needed, use a different Apple ID or device to avoid linking to the old account