How can I clone a text that’s inside a and paste it in the same ?

I’m trying to create a function that would copy the <p> text and paste it within the same div (duplication) on click.

I’ve tried a couple of methods, none of them worked, unfortunately.

function duplicate() {
  let clone = document.querySelector('.header p').cloneNode(true);
  document.querySelector('.header').appendChild(clone);
}

<div class='header'>
  <p onclick="duplicate();">Text</p>
</div>