Please have a look at the following example:

https://dojo.telerik.com/eRajAbIX/

Steps to reproduce:

1. Select a single word in the editor, e.g. ipsum.

2. Click the Clean formatting button.

3. The background color of the selected word was not changed.

Currently, the cleanFormatting tool works for removing the format from the entire element and does not split the content if a word is selected. This could be enhanced so that the selected part of the element is split into a new nested element whit no formatting.