Do you program any elisp, at all, ever?

;; Elisp go-to-definition with M-. and back again with M-,
(autoload 'elisp-slime-nav-mode "elisp-slime-nav")
(add-hook 'emacs-lisp-mode-hook (lambda () (elisp-slime-nav-mode t)))
(eval-after-load 'elisp-slime-nav '(diminish 'elisp-slime-nav-mode))

Then you need to M-x package-install elisp-slime-nav-mode.

It lets you jump to the definition of a function with M-., and back again afterwards with M-,.

That last line says that we want elisp-slime-nav-mode to continue doing its work for us, but we no longer want to be reminded of it.