Display custom excerpt

custom-excerpt.txt

1) Create a textarea field and attach it to page - https://cl.ly/060d1cd4d38b
2) Add text to your textarea field - 
3) Add below CSS to hide the default excerpt - 

.uael-post__excerpt {
	display: none;
}

.custom.uael-post__excerpt {
	display: block;
}

4) Add the below filter in your functions.php
function excerpt_before( $post_id, $settings ) {
	?>
    <div class="custom uael-post__excerpt">
    	<?php echo get_field( 'page_excerpt', $post_id ); ?>
    </div>
    <?php
} 
add_action( 'uael_single_post_before_excerpt', 'excerpt_before', 10, 2 );

Note - Please replace the 'page_excerpt' with the ID of your custom field.

These steps will hide the original excerpt while displaying custom from the field.