function sqr_group_excerpt_length($group) {
    if(bp_is_active()) {
        if (bp_is_group()) {
            if (strlen($group) > 10) {
                $str = substr($group, 0, 101) . '';
                return $str;
            }
        }
    }
}
add_filter('bp_get_group_description', 'sqr_group_excerpt_length',10,1);