As mentioned in the comments, defining and using an atom in a function is a totally non-clojure way of solving the question which makes it all the more difficult to solve. You should get familiar with the concept of immutability and higher order functions like map, filter, reduce, etc.
The code below gives you what you want.
(def fib1
(fn [n]
(cond
(= n 0) 1
(= n 1) 1
:else (+ (fib1 (dec n)) (fib1 (- n 2))))))
since this gives you just nth Fibonacci number, you should take + map with it if you want to get what you want.
(take 10 (map fib1 (range))) => (1 1 2 3 5 8 13 21 34 55)
take a look at this beautiful solution I found on internet.
(def fib-seq-iterate (map first (iterate (fn [[n m]] [m (+ n m)]) [0 1])))
This returns a lazy sequence, which can be called with
(take 5 fib-seq-iterate) => (0 1 1 2 3)