Think of it like an actor on stage who is playing a very dramatic role. They might use a lot of big gestures, loud voices, and exaggerated expressions to get their point across. This is "hamming it up."
Here are some examples:
* "He hammed it up for the camera, trying to make it seem like he was a real hero." He exaggerated his actions to make himself look more heroic.
* "She hammed it up in her performance, making the audience laugh with her over-the-top antics." She used exaggerated gestures and expressions to get a comedic effect.
The saying comes from the idea that ham actors (actors who are considered to be bad or overacting) "ham it up" by overplaying their roles.