A cleaning unit for cleaning foreign matter from a cover, in particular a cover of a transmitter/receiver window of an environment sensor, including at least one movable wiper blade, which is arranged so as to wipe off foreign matter such as water or dirt on the cover by movement along the cover. For this purpose, the wiper blade touches the cover for example with one or multiple rubber lips. The wiper blade is positioned in an inclined manner with respect to a direction of movement of the wiper blade and is thus movable in such a way that a force exerted by the moved wiper blade on the foreign matter has a component in the direction of the force of gravity. Also described is a related device for sensing the environment as well as a method for cleaning a cover.