yes and no.
not in the traditional sense, because a drop always displays one of the "list of values".
So what I usually do is add a value to the top of the list (more settings tab) with some sort of
[ select item ]
type entry.
(you can even set the css of this entry to grey if you like.)
so it's not a place-holder, because it's always visible in the list - but it does prompt the user to select something.
cheers
Bruce