EDIT: One interesting observation (from the outsider's perspective) - As I see, Clojure encourages use of primitive/language-provided data structures such as maps, lists, etc.. instead of creating your own abstractions and "inventing languages" (this is mentioned in a negative context, in Clojure docs). This is radically different approach compared to e.g. SICP, where creating many mini languages is actually encouraged. I personally find Clojure approach messy and unstructured (Also browsing a code in the wild).
Anyway, as I can tell, Clojure has enough support to create well structured abstractions.
Creating abstractions shouldn't be the most advanced topic in the language.