<svg xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink'>
<defs>
    <rect x='50' y='150' width='50' height='50' id="rect" fill='none' clip-path='url(#clipPath_1)'/>
</defs>

<clipPath id='clipPath_0'>
  <rect x='50' width='50' height='50' clip-path='url(#clipPath_0)'/>
</clipPath>

<clipPath id='clipPath_1'>
  <use xlink:href="#rect"/>
</clipPath>

<!--
Spec: clip-path: If the IRI reference is not valid (e.g it points to an object that doesn't exist or the object
                 is not a ‘clipPath’ element) the ‘clip-path’ property must be treated as if it hadn't been specified.
-->

<rect x='50' width='100' height='100' fill='blue'/>
<rect x='50' width='100' height='100' fill='green' clip-path='url(#clipPath_0)'/>

<rect x='50' y='150' width='100' height='100' fill='blue'/>
<rect x='50' y='150' width='100' height='100' fill='green' clip-path='url(#clipPath_1)'/>
</svg>