How to kill the content of a list instead of the list itself?

I have a list containing some variables, for example:

mylist : [a,b,c,d]

a, b, c, d may have or not assigned values. That list can have much more
elements than the four in the example.
I would like to kill a, b, c, d by giving kill mylist as argument. But

kill(mylist)

only kills the variable mylist and leaves unchanged a, b, c, d. Actually,
kill can kill list content without killing the list itself, like:

kill(labels)

where labels, arrays, functions are special list variables, and they are not
deleted. So I'm guessing I should give mylist some special properties, maybe
using declare or something similar...

Any suggestion?

Thanks
Stefano