This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible
Masks are kinda similar. I used one to cut a circle out of a square so that you can see through it.
<rect width="14vw" height="14vw" fill="white"/>
<circle cx="7vw" cy="7vw" r="6vw" fill="black"/>
<rect mask="url(#spinnerHole1") id="spinMove"/>