My suggestion is to do this using code. IF your using D7, try following code in any custom module or in a basic page. 

    //Use a query to get all nodes of your particular content type.

    $results = db_query("SELECT nid FROM node WHERE type = 'your-content-type'");
    $nids = array();
    foreach($results as $result){
      $nids[] = $result->nid;
    }
    
    foreach($nids as $nid){ // use for loop for testing
      $node = node_load($nid);
      foreach ($node->field_international_activity[LANGUAGE_NONE] as $key => $value) {
       // Build array of field collection values.
       $field_collection_item_values[] = $value['value'];

       // Unset them.  
       unset($node->field_international_activity[LANGUAGE_NONE][$key]);
      }

    // Delete field collection items.
    entity_delete_multiple('field_collection_item', $field_collection_item_values);
    node_save($node);
    }

For more details please refer [link1][1], [link2][2]

This code is not tested, first just try for a single node by using a **for loop** instead of **foreach**.


  [1]: http://drupal.stackexchange.com/questions/68765/how-to-properly-delete-a-field-collection
  [2]: https://www.drupal.org/node/2684165