You may need js to help with, modify it at your will and place it in Advanced->Custom code injection
<script>
var addedText = '<p class="" style="white-space:pre-wrap;"><em>For more on this bag head to @blaiserubyloves instagram for more in depth videos and pictures of this bag and others, where you will see more on condition, imagery of the bag and styling tips. </em></p>';
document.addEventListener('DOMContentLoaded', function() {
if ( document.querySelector(".ProductItem-details-excerpt") ) {
document.querySelector(".ProductItem-details-excerpt").insertAdjacentHTML("beforeend", addedText);
}
});
</script>
