Cannot remove green background of added clip to the existing video when the final video is exported.

On my video timeline I posted an animation of a "Subscribe" clip that I found online. This animation by itself is on a green background but when I place this animation over my video, it blends with the existing video background and it's fine (green background disappears). However, when I go to Export and Save this video at 4K, the final video shows the little animation on the green background over my existing video. Is there a way to have this green background for my animation not show when I save the video? See attached screenshot. Please help. Thank you.