Binary search algorithm in Clojure
Your implementation is pretty similar to this one: https://programming-pages.com/2012/01/31/binary-search-in-clojure/

I think the overall algorithm is OK.
You should avoid using def inside function - that should be used only for global top-level vars -> use let instead.
Also, the code formatting is incorrect - use 2 spaces and proper indentation:

(defn log-search
  [elements elem-to-find]
  (loop [left 0
         right (dec (count elements))]
    (when (&lt;= left right)
      (let [m (int (Math/floor (/ (+ left right) 2)))
            actual (nth elements m)]
        (cond
          (= actual elem-to-find) m
          (&lt; actual elem-to-find) (recur (+ m 1) right)
          (&gt; actual elem-to-find) (recur left (- m 1)))))))