How to delete(or kill) the current word in emacs?

The Emacs way to remove the word one is inside of to press M-backspace followed by M-d. That will kill the word at point and save it to kill ring (as one unit).

If the cursor is at the beginning or after the end of the word, only one of the two is sufficient. An Emacs user will typically move between words using commands such as forward-word (M-f) and backward-word (M-b), so they will be at the word boundary to begin with and thus rarely need to kill the word from the inside.

You could use this as a framework for killing various kinds of things at point:

(defun my-kill-thing-at-point (thing)
  "Kill the `thing-at-point' for the specified kind of THING."
  (let ((bounds (bounds-of-thing-at-point thing)))
    (if bounds
        (kill-region (car bounds) (cdr bounds))
      (error "No %s at point" thing))))

(defun my-kill-word-at-point ()
  "Kill the word at point."
  (interactive)
  (my-kill-thing-at-point 'word))

(global-set-key (kbd "s-k w") 'my-kill-word-at-point)

You can do that by moving to the beginning of the word (if not standing there already) by M-b, then deleting it with M-d. You can then press C-y to put it back. If you want to automate it, you can create a short elisp function and assign it to a key:

(global-set-key [24 C-backspace] ; C-x C-backspace
                (lambda () (interactive)
                  (save-excursion
                    (backward-word)
                    (kill-word 1)
                    (yank))))