How do I "undo" or "unclean" a file?

If TuneUp incorrectly "cleans" a song, you have the option of restoring it's original metadata at any time using the "undo" feature. 

Underneath the Clean tab, click on the Undo icon.

1. In iTunes, find the song(s) you want to "undo." Highlight them, and drag them into the "undo" window.
2. Tuneup will display the track's original information. Click on the "Revert" button to process the changes.