The term PART OF A DRAIN can be broken down into two crossword solutions: TRAP (4 letters) and GASTRAP (7 letters). A TRAP is a curved section of pipe that is designed to hold water, preventing sewer gases from entering the home. A gastrap is a type of TRAP that is designed to prevent the backflow of gas from entering the home. Both traps are important components of a drain system, as they help to keep the air in the home safe and free from hazardous gases.