(defmacro define-accessor-alias (alias (&rest lambda-list)  original)
  (let ((ll  (parse-lambda-list lambda-list  :ordinary)))
    `(progn
       (defun ,alias ,lambda-list (,original ,@(make-flat-argument-list ll)))
       (defun (setf ,alias) (new-value ,@lambda-list) (setf (,original ,@(make-flat-argument-list ll)) new-value)))))

(pprint (macroexpand-1 '(define-accessor-alias kar (cons) car)))
--> (progn (defun kar (cons) (car cons)) (defun (setf kar) (new-value cons) (setf (car cons) new-value)))

(pprint (macroexpand-1 '(define-accessor-alias subsequence (sequence start &optional end) subseq)))
--> (progn (defun subsequence (sequence start &optional end) (subseq sequence start end))
           (defun (setf subsequence) (new-value sequence start &optional end) (setf (subseq sequence start end) new-value)))