field template for a specific content type
Try "-" in the contact type name like field--field-description--festivals-events.tpl.php  

[Edit]
You may also need a template suggestion in your theme.

function mytheme_preprocess_field(&amp;$variables) {
    if($variables['type'] == 'festivals-events'){
        if($variables['element']['#field_name'] == 'field_description') {
            $variables['theme_hook_suggestions'][] = 'field__field_description__festivals_events';
        }
    }
}