What's off to the side in a selfie

ARM

Think about what you extend to hold the camera just out of the frame.

In a selfie, you usually hold the phone out at arm’s length to fit yourself in the frame. The clue plays on the idea that your "arm" is literally off to the side—both in the photo and as the body part extending to take the shot. It’s a straightforward hint where the answer is the physical thing you’d see sticking out in most selfies.