Something

(defun quicksort_r(lst)
  (if (endp lst)
      lst
      (append 
       (quicksort_r 
	(remove-if-not (lambda (x) (<= x (first lst))) (rest lst)))
       (list (first lst))
       (quicksort_r 
	(remove-if-not (lambda (x) (> x (first lst))) (rest lst))))))