For example, the instance I am trying to remove is called "Foe".
Actor foe;
foe = getOneObjectAtOffset (0,0,Foe.class);
if (foe !=null)
{
World world;
world = getWorld();
world.removeObject(foe);
Like I asked in another question, you must declare it before you use the "world.removeObject(foe);", which seems pretty silly to me.