I had somebody request that me how do this a day or two ago and I didn’t know how. Be that as it may, in the wake of perusing a portion of the WordPress Codex I could make sense of it. To reject particular classes from your RSS channel simply add the accompanying code scrap to your subject’s functions.php record.
As usual, ensure it is between PHP labels. Furthermore, if the topic you are utilizing does not have a functions.php record, simply make on yourself and include the above code bit after an opening PHP tag.