Can I hide a swear word or make a clean version?

Changing the lyrics only changes the text. Your video still uses the audio file you uploaded.

Change the written words

1. Check the sync against the words actually sung.
2. Open 'More tools' on Sync and select the line.
3. Choose 'Edit' and change the spelling.
4. Keep the same number of words if you want to keep the existing word timings.
5. Play that line again and check your chosen style.

To change the audio, make a clean audio edit first and start a new project with that file. A different recording can need a new sync charge.

'Ad-libs' set to 'Hide' hides marked backing words on screen. It does not remove their sound.

There is no single masking character guaranteed across every font. Preview your edited line and choose a font that can draw it. A text edit does not make the audio clean.