Is Clojure/Clojurescript Go to Declaration works ?

Yes, it needs to be connected to a REPL and current buffer to be evaluated.

@scknkkrer cider-find-var is the command I assume you are asking about. As has been mentioned, it only works with the REPL running (and you may need to evaluate your own function definitions before it finds them)

You can also use dumb-jump-go which does not need the REPL. As the name suggests, it simply looks for matches in the project, so may give a wider set of matches

suggestions for navigating Clojure code: https://practicalli.github.io/spacemacs/navigating-code/