Most Cursive IDE nREPL solutions point to the Figwheel approach which good but is a little cumbersome.
You can also use piggieback (which Figwheel also uses).
Update your project.clj as such:
(defproject blah "0.0.1"
:profiles {:dev {:dependencies [[com.cemerick/piggieback "0.2.2"]]}
:repl-options {:nrepl-middleware [cemerick.piggieback/wrap-cljs-repl]}})
Then simply create a Clojure REPL Run/Debug configuration using the "Run nREPL with Leiningen` option.
Note if you want an async handler, you will need to use Figwheel instead and hook into a more featured Javascript engine.