Drop Down Menu for pages

Hi there, I am wondering If anybody could help with my problem. On my site I set up a rudimentary system to sort my pages, setting one page as a parent (named: portfolio) and then placing the rest of my pages underneath as child pages. This means that if I click on the parent page it takes me to that page.

What I would like to do is have just a drop down menu so that if someone clicked on portfolio it wouldn’t take them to that page if that makes sense

Here is the site in question http://www.depressedcat.com