Wader, e.g. is a term used to describe a type of bird that typically wades in shallow water. The crossword solution for this term is BOOT, which is a four letter word. A BOOT is a type of footwear that is designed to protect the foot and ankle from water, mud, and other elements. This makes it an appropriate solution for the term wader, e.g., as it is similar to the type of protection that a wading bird would need when in shallow water.