The crossword solution for the term WORK ON, AS A BONE is GNAW, which is a four letter word. GNAW is an action verb that means to chew on something persistently, usually with the teeth. This term is often used to describe the behavior of animals, such as rodents, who will GNAW on bones to get to the nutritious marrow inside. It can also be used to describe the behavior of humans, such as when someone is nervously biting their nails.