A coffee filter is a device used to separate coffee grounds from brewed coffee. The groundskeeper is responsible for the maintenance of the grounds of a property, such as a golf course, park, or estate. This includes mowing, trimming, fertilizing, and other tasks related to keeping the grounds in good condition. In this crossword puzzle, the term 'groundskeeper' is used to describe the 13-letter solution to the clue 'coffee filter.'