В рубриках нужно выводить только список подрубрик без

В файл functions.php активной темы добавьте код:

function remove_post_from_subcat( $where ){
    global $wp_query, $wpdb, $wp_version;

    // Fire off if we're viewing a category archive
    if ( is_category() ){

        // Get children categories of current cat if they exist
        if ( $excludes = get_categories( "child_of=" . $wp_query->get( 'cat' ) ) ) {

            // For each child, add just the ID to an array
            foreach ( $excludes as $key => $value ) {
                $exs[] = $value->term_taxonomy_id;
            }

        }

        // If array exists, remove posts in child categories from query.
        if ( isset( $exs ) && is_array( $exs ) ) {

            // WP Query changed in 3.1
            if ( version_compare( $wp_version, 3.1, '<' ) )
                $where .= " AND " . $wpdb->prefix . "term_taxonomy.term_id NOT IN ( ". implode( ",", $exs ) . " ) ";
            else
                $where .= " AND " . $wpdb->prefix . "term_relationships.term_taxonomy_id NOT IN ( ". implode( ",", $exs ) . " ) ";
        }
    }

    return $where;

}

add_filter( 'posts_where', 'remove_post_from_subcat' );