As Corel Vector is a vector tool, there isn’t some kind of eraser to remove some portions of an image, but that is still possible with other features, like Clip.
Create a shape with a drawing tool, outlining the area of an image that you want to keep. In this example, the leaf will kept and the background removed.
Clip the image with the shape, creating a Mask shape. If you want, toggle the border’s visibility.
If you want the opposite effect, in this case removing the leaf and leaving the background, you will create a mask with a hole. Create a rectangle of the same size as the background and use the shape created with the drawing tool to create a Compound Shape, removing the shape from the rectangle.
Then, you need to convert the resulting Compound Shape to a Path (or + + ) because Compound Shapes can’t be clipped. Next, clip the image to your just-created mask with the hole in the middle. Toggle the border’s visibility if necessary.