As seen on http://blog.japila.pl/2011/01/dynamically-redefining-classpath-in-clojure-repl/ see also add-classpath (depreciated) https://clojuredocs.org/clojure.core/add-classpath and addURL

dynamic-change-classpath-in-repl.clj

user=> (System/getProperty "java.class.path")
"/some/path/clojure/clojure.jar"
user=> (System/setProperty "java.class.path" ".:/some/path/clojure/clojure.jar:/some/other/lib.jar")
".:/some/path/clojure/clojure.jar:/some/other/lib.jar"
user=> (def cl (-> (Thread/currentThread) (.getContextClassLoader)))
#'user/cl
user=> cl
#<DynamicClassLoader clojure.lang.DynamicClassLoader@19c5466b>
user=> (-> cl (.addURL (java.net.URL. "file:///some/other/lib.jar")))
nil
user=> (import  '(com.google.inject Guice AbstractModule))
com.google.inject.AbstractModule