Every Uccello Kettle comes with a stainless-steel gauze filter. It is there to prevent limescale/mineral build-up that could end up in your drink. Limescale can give your drink a powdery taste.
When cleaning it, please remember that it can be easily removed for cleaning. You can clean your filter with a mild detergent and damp cloth or by using a white vinegar bath and rinse clean.
To help you remove and refit your yours, here is a demonstration video: