The crossword solution for the term 'SIDE FLAP' is 'EAR'. An EAR is a flap of skin on either side of the head that is used to hear sound. It is made up of three parts: the outer EAR, the middle EAR, and the inner EAR. The outer EAR consists of the visible part of the EAR, the pinna, and the EAR canal. The middle EAR contains the eardrum and three tiny bones called ossicles. The inner EAR contains the cochlea, which is responsible for converting sound waves into electrical signals that are sent to the brain.