If you want to clear the current namespace of all temporary variables and functions you declared you can use this one liner (or make a function of it) :
(map #(ns-unmap *ns* %) (keys (ns-interns *ns*)))
or
(ns myutil)
(defn ns-clean
"Remove all internal mappings from a given name space or the current one if no parameter given."
([] (ns-clean *ns*))
([ns] (map #(ns-unmap ns %) (keys (ns-interns ns)))))
(ns mytest)
... make loads of junk ...
(myutil/ns-clean)
... great!!! I can now make all new junk ...
It does not claim to give you a squeaky clean namespace, just one with less of the junk which usually accumulates in a typical repl session.
Use with caution : do not pull the rug from under your feet!