delete-entity-fields

/**
 * Implements hook_uninstall().
 *
 * Deletes the NUTS regions variables.
 * Deletes the NUTS regions vocabulary (fields and data).
 */
function nuts_regions_uninstall() {
  $t = get_t();
  variable_del('clients');
  drupal_set_message($t('NUTS regions: NUTS regions was uninstalled from your site.'));

  // Deletes the taxonomy term.
  $vocabulary = taxonomy_vocabulary_machine_name_load('nuts_regions');
  if ($vocabulary) {
    $vid = $vocabulary->vid;
    taxonomy_vocabulary_delete($vid);
  }

  // Deletes the custom fields.
  $fields = array(
    'nuts_level',
    'nuts_id',
    'nuts_code',
    'nuts_country',
    'nuts_description',
    'nuts_remark',
  );
  foreach ($fields as $field) {
    field_delete_field($field);
    if ($instance = field_info_instance('taxonomy_term', $field, 'nuts_regions')) {
      field_delete_instance($instance);
    }
  }
  field_purge_batch(count($fields));
  drupal_set_message($t('NUTS regions: NUTS regions vocabulary has been deleted from your site.'));
}