add_action( "propertyhive_property_imported_expert_agent_xml", 'use_advert2_as_summary', 10, 2 );
function use_advert2_as_summary($post_id, $property)
{
    if ( isset($property->advert2) && (string)$property->advert2 != '' )
    {
        $my_post = array(
            'ID'             => $post_id,
            'post_excerpt'   => (string)$property->advert2,
        );

        // Update the post into the database
        $post_id = wp_update_post( $my_post );
    }
}