<svg xmlns="http://www.w3.org/2000/svg">
<clipPath id="clip1">
  <!-- nothing should be visible, containers are not allowed in clipPath -->
  <g>
    <rect width="100" height="100"/>
  </g>
</clipPath>
<rect width="200" height="200" fill="green" clip-path="url(#clip1)"/>
</svg>