how do I clean boot a wundows phone running 8.1

Solution
If you mean full wipe back to factory fresh settings for Lumia, with the device powered off.

Hold volume down and insert power cable until you see exclamation mark comes up on the screen.

Enter this button combination, Volume Up, Volume Down, Power, Volume Down.

Phone will reboot and reinstall fresh version foe WP81, may take a few minutes.
If you mean full wipe back to factory fresh settings for Lumia, with the device powered off.

Hold volume down and insert power cable until you see exclamation mark comes up on the screen.

Enter this button combination, Volume Up, Volume Down, Power, Volume Down.

Phone will reboot and reinstall fresh version foe WP81, may take a few minutes.
 
Solution