You may want a top level menu item that does NOT link to any page. In that case, you will want to create a Custom Link menu item.
1. Log in as an Admin and go to Appearance > Menus
2. On the left, create a Custom Link
URL: Include a hashtag which will render the item without a link.
Link Text: Add the text you want to see as the menu parent.
3. Use this new Custom Link as the parent to any subpages you want listed underneath it within the menu.
4. You're done, once you click Save Menu