An OUTHOUSE is a small structure, typically located outside of a home or other building, which is used as a toilet. It is usually a simple wooden or metal shed with a hole in the floor and a seat over the hole. The term 'OUTHOUSE' is derived from the fact that it is often located away from the main house. TENT is an appropriate four-letter solution for this crossword clue, as tents are often used as temporary outhouses when camping or in other outdoor settings.