Possible Clues:

• 'Please God 16 down never goes off again like this (4,4)'
• It's grave after a mob trashed device
• Fat Man or Little Boy
• *Leo Szilard and Joseph Rotblat
• A male duck nibbling crest of milkweed that goes up like a mushroom
• Einstein referred to his endorsement of it as 'one great mistake'
• Manhattan Project project (2 words)
• Rush after a cat -- it could cause immense damage
• All back graduate catching gang leaders marching on TCD - the fall-out from this is deadly
• Explosive device with rapid release of nuclear energy