You can view the help of a lisp function with C-h f, then hit enter on the underlined file name.
Any way to do this with a customized keystroke?
(global-set-key "\C-h\C-f" 'find-function-at-point)
find-function-other-window
or find-function-other-frame
or find-function
.
Here are two ways. The first was suggested by @lawlist in a comment, above. Wrt the second: this is why Emacs tags were invented: to go immediately to a function definition.
find-function
-- bind it to any key you like. I bind it to C-x F
(i.e., C-x S-f
).
M-.
(command find-tag
), after building a TAG file -- see (elisp) Tags
.