The term ONE WAY IN can be solved by the crossword solutions DOOR and SIDEENTRANCE. The word DOOR is a four letter word that refers to an entrance or exit to a building, room, or other enclosed space. The word SIDEENTRANCE is a twelve letter word that refers to an entrance or exit to a building, room, or other enclosed space that is located on the side of the structure. Together, these two words describe a situation where there is only one way to enter or exit a certain area.