Go to Appearance > Menus from the admin dashboard.
Scroll down and expand the Links section on the left.
For the URL, just put in #, nothing else. For Link text, put in Video.
Click the Add to Menu button, then drag & drop the new menu item on the right to where the existing Video menu item is.
Drag & drop the sub menu items from the old Video menu item to the new Video menu item.
Delete the old Video menu item.
Click the Save Menu button.
When users click on the Video menu item, nothing will happen, but the submenu items will still work.
If you really want to get fancy, inspect the menu item with a web debugging tool like Firebug or Chrome Developer Tools, find out the ID of the new menu item, then add some CSS to prevent the cursor from turning into a hand pointer on hover.