If you have an init.clj file in ~/.lein, and that file prints out any text, the clojure-jack-in procedure will attempt to evaluate it as elisp at the beginning of the swank buffer.
To reproduce:
create an iniit.clj file in ~/.lein and have it execute (println "Loaded init.clj")
open emacs and type M-x clojure-jack-in
emacs will eventually report "Error: Symbol's value as a var is void: Loaded"
open the swank buffer and note the text "Loaded init.clj" at the top of the buffer.
If you have an init.clj file in ~/.lein, and that file prints out any text, the clojure-jack-in procedure will attempt to evaluate it as elisp at the beginning of the swank buffer.
To reproduce: