Select it and hit delete.
I tried doing that but it didn't work - with your repy, I went back and tried again and on about the 5th try, I was able to select "cut" from the edit menu (which had been grayed out).
Maybe it's locked.
Select your graphic and look at the "Object -> Lock" menu item. It's it's disabled, then the item is locked.
Choose "Object -> Unlock All on Spread" to unlock it.