When we say that an actor "chews up scenery", we mean that they overact or perform in an exaggerated manner in order to draw attention to themselves. There are many other phrases that can be used to describe this kind of behavior. Some synonyms for "chews up scenery" include "hamming it up", "scene stealing", "showboating", and "mugging for the camera". These expressions all convey the idea that the actor is being excessive in their performance, drawing attention away from the story or other actors. While some performers can excel with this approach, it can also come across as fake or distracting.