Is there a chance to flatten/merge the clipPath, e.g. this SVG:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
  <defs>
    <clipPath id="a">
      <path fill-opacity=".7" d="M102.4 0h708.7v708.7H102.4z"/>
    </clipPath>
  </defs>
  <g fill-rule="evenodd" stroke-width="1pt" clip-path="url(#a)" transform="translate(-74) scale(.722)">
    <path fill="#e80000" d="M0 0h1063v708.7H0z"/>
    <path fill="#fff" d="M0 0h1063v354.3H0z"/>
    <path fill="#00006f" d="M0 0l529.7 353.9L0 707.3V0z"/>
  </g>
</svg>

By "flatten/merge" do you mean you want less code?  No, not that I know of.

But if it's a vector object, you might be able to use a path operation, rather than clipping.  That's a simple enough image, it could be easily edited to the size you need, without using clipping.

Or another note.  The page size is identical to the clipping path.  So the page border itself might act as clipping in certain situations.