The arguments presented to a macro don't have to be valid code. Your "function evaluating functions" are all individually valid functions you've composed at runtime.

    (defmacro foo [code] ,,,)
    (foo "<some totally different language in a string>")

=> actual, compiled Clojure function built up by `foo` parsing the string, producing a Clojure list, and calling `(eval the-list)` and returning it.

I passed a string to `foo` in the example, but it could actually be anything the Clojure reader can parse even if it is semantically invalid—arbitrary Clojure data.