Wordbox in Clojure

wordbox.clj

(defn get-wordboxes [word]
  "Given a word like 'cat', make all possible wordboxes in English.  Here's an example wordbox:
  
   CAT
   O*E
   GUN
  
   Note that the words 'cog', 'ten' and 'gun' come from the word 'cat'.

   The code below is too slow for words of four-letters-long or longer.  I was hoping to make a full-fledged
   web app from this code, but it would be too slow in most instances.  I'm abandoning the effort and posting 
   the working code for reference.

   The list of words used is the Official Scrabble Players Dictionary (English) 3rd edition, available as a text
   file in my npr_sunday_puzzle_solutions repository in Github.
  "
  (let [word-arrays
         (->> "/home/mitchells/Desktop/npr_sunday_puzzle_solutions/resources/ospd3.txt"
              slurp
              clojure.string/split-lines
              (map (comp seq char-array))
              set)
        words-same-length (filter (comp (partial = (count word)) count) 
                                  word-arrays)
        words-by-first-letter (group-by first words-same-length)]
    (for [w1 (get words-by-first-letter (first word))
          w2 (get words-by-first-letter (last word))
          w3 (filter #(and (= (last w1) (first %))
                           (= (last w2) (last %))) 
                     words-same-length)
          :when (and (not= w1 w2)
                     (not= w1 w3)
                     (not= w2 w3)
                     (not= (apply str w1) word)
                     (not= (apply str w2) word)
                     (not= (apply str w3) word))]
      [w1 w2 w3])))