How to activate a Div on hover of a menu item in wordpress

Wishing to hover over a menu item and with CSS only, have a Div change to show some "special effect." The Special Div could show a picture or it could appear to descend from above and cover the menu item or highlight it in some way....

If the Div is covering the Menu Item with an Opacity, when the Div is clicked, it can be as if, or such that, the Menu Item is clicked. Or if the Div is not covering the menu item, the div could not be like a button. It would depend on what is best for each Div, but the one here will be covering the Menu Item and must act as if the menu item were clicked.