sets.clj

user> sets
[#{:a :c :b} #{:c :d} #{:f :e}]
user> (reduce (fn [curr new]
                  (if-let [match (first (filter #(some new %) curr))]
                    (map #(if (= match %)
                            (union new %)
                            %)
                         curr)
                    (conj curr new)))
              [] sets)
(#{:f :e} #{:a :c :b :d})