Improve the docstring for clojure-defun-indents

Author: Malabarba

clojure-mode.el

@@ -1279,10 +1279,11 @@ Requires the macro's NAME and a VALUE."
   "List of additional symbols with defun-style indentation in Clojure.
 
 You can use this to let Emacs indent your own macros the same way
-that it indents built-in macros like with-open.  To manually set
-it from Lisp code, use (put-clojure-indent 'some-symbol :defn)."
+that it indents built-in macros like with-open.  This variable
+only works when set via the customize interface (`setq' won't
+work).  To set it from Lisp code, use
+     (put-clojure-indent \\='some-symbol :defn)."
   :type '(repeat symbol)
-  :safe #'listp
   :set 'add-custom-clojure-indents)
 
 (define-clojure-indent