(find-var sym)
Returns the global var named by the namespace-qualified symbol, or nil if no var with that name.
user=> (find-var 'clojure.core/map)
#'clojure.core/map
user=> (find-var 'clojure.core/qwerty)
nil
user=> (find-var 'map)
IllegalArgumentException Symbol must be namespace-qualified clojure.lang.Var.find (Var.java:150)