Clear custom field when new tag is added

Could you do something like this?

function tag-added-script()
{
    ?>
<script>

jQuery(function($) {
    $('.tagadd').click(function() {
        // Run Your Jquery Here
        alert('test');
    });
});
</script>
    <?php
}
add_action( 'admin_head', 'tag-added-script' );

The above will react whenever the “tagadd” button is clicked. Theoretically you could then grab the custom field ID and clear it via jquery.