M-m in Spacemacs Emacs mode (holy mode) opens the mnemonic which key menu to guide you through all command key bindings M-m m or M-RET show the key binding for the current major mode, e.g Clojure. This provides the same Clojure key bindings as , in Evil mode (vim style) editing M is the meta key, usually Alt on Linux and Mac Option RET is the Return or Enter key

I think most of the default Cider key bindings are also available, e.g. those documented at https://docs.cider.mx/cider/index.html