user=> (defn init [] (defn add5 [x] (+ x 5)))
#'user/init
user=> (add5 1)

IllegalStateException Attempting to call unbound fn: #'user/add5  clojure.lang.Var$Unbound.throwArity (Var.java:43)
user=> (init)
#'user/add5
user=> (add5 1)