Fatal error: Call to undefined method EntityListWrapper::delete()

I am getting the error Fatal error: Call to undefined method EntityListWrapper::delete() with this code:

            // Delete the Actuals.
            if ($tracker->field_related_actuals->value()) {
              $tracker->field_related_actuals->delete();
              drupal_set_message(t('Actual costs record deleted.'));
            }

Why is this invalid?