<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
  <rect id="circle" x="50" y="50" width="100" height="100"/>
</defs>
<clipPath id="clip1">
    <use xlink:href="#circle"/>
</clipPath>
<rect width="200" height="200" fill="green" clip-path="url(#clip1)"/>
</svg>