The term CANVAS FOR TATS is a crossword solution that refers to the SKIN, which is a four-letter word. SKIN is the outermost layer of the human body and is composed of two main layers: the epidermis and the dermis. It serves as a protective barrier against environmental factors, such as bacteria, viruses, and ultraviolet radiation. SKIN also helps regulate body temperature and plays an important role in the production of vitamin D.