clip-path with Firefox problems

Question

I’m using the clip-path technique to make a polygon in a certain area of the site:

.cliped {
    -webkit-clip-path: polygon(0% 0%, 100% 0%, 100% 100%, 0% 75%);
    -ms-clip-path: polygon(0% 0%, 100% 0%, 100% 100%, 0% 75%);
    clip-path: polygon(0% 0%, 100% 0%, 100% 100%, 0% 75%);
    clip-path: url("#polygon");
}

But this way it doesn’t work in Firefox. With a quick search I found out that Firefox needs an addition (web standards my **) to SVG:

<svg width="0" height="0">
    <defs>
        <clippath id="polygon">
                        <polygon points="0 0, 1 0, 1 1, 0 0.75"></polygon>
        </clippath>
    </defs>
</svg>

And as you can see here did not solve bullhufas.

Someone there is qualified?