Stylize parent element CSS

Question

I would like to know how to style an element according to his son.

.content p {
  text-indent: 20;
}

<div class="content">
  <p>1</p>
  <p>2</p>
  <p>
    <iframe></iframe>
  </p>
  
  <!--I have to modify this paragraph-->
  <p>4</p>
</div>

What do I need to do, is to modify the paragraph that has the iframe (text-indent: 0).

Answer 1

The best is to write something like

<p class="custom">...</p>

Then add style with

p.custom{
    /* Your styles here */
}