Clojure filter that works with deep nested structures

filter-nested.clj

(defn filter-nested 
  [pred xs]  
  (loop [r []
         ys xs]
    (let [k (first ys)
          _ (print k)]
      (cond
        (not (sequential? k))
        (cond
          (= [] ys) r
          (pred k) (recur
                    (conj r k)
                    (rest ys))
          :else (recur r
                       (rest ys)))
        (empty? ys) r
        (sequential? k)
        (recur
         (conj r (filter-nested pred k))
         (rest ys))))))