WordPress, by default, don’t allow shortcodes to be executed inside custom fields. While, if in case, you want to do it so, then this can be done by using the following snippet below. Simply paste the snippet to the page where you wish to display the results of the shortcode. While doing this, make sure you do change your_custom_field_here to the name of your selected custom field.
<?php echo apply_filters('the_content', get_post_meta($post->ID, 'your_custom_field_here', true)); ?>
Snippet Source/Credit: Snipplr