That probably means the clojure block is returning nil as the value. I don't know what it means to return something in clojure, but here is what you have to do with Python, for example.

#+BEGIN_SRC python :results value code
[1, 2, 3]
#+END_SRC

#+RESULTS:
#+begin_src python
None
#+end_src

You have to explicitly return a value to see it.

#+BEGIN_SRC python :results value code
return [1, 2, 3]
#+END_SRC

#+RESULTS:
#+begin_src python
[1, 2, 3]
#+end_src

John

-----------------------------------
Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803

@johnkitchin
http://kitchingroup.cheme.cmu.edu

On Thu, Jun 24, 2021 at 10:31 AM Johannes Brauer <brauer@nordakademie.de> wrote:

What about :results code
The default is a elisp code block so you get syntax coloring

That works fore lisp:

#+begin_src elisp :results code

(list 1 2 (+ 1 2))

#+end_src

#+RESULTS:

#+begin_src elisp

(1 2 3)

#+end_src

But with Clojure I get

#+begin_src clojure :results code

(list 1 2 (+ 1 2))

#+end_src

#+RESULTS:

#+begin_src clojure

nil

#+end_src