Related Clues:

• Manhattan Project goal
• Big blast maker, for short
• It was used to discover fermium
• Cloud maker
• The first fell on Hiroshima
• It first fell on Hiroshima
• The first one fell on Hiroshima
• Go off after 22 across in a very big way
• 'Please God 16 down never goes off again like this (4,4)'
• Drop __ (announce startling news)
• Cloud producer, informally
• Trinity test subject
• It can kill so many first off, Pat ... ring the doctor, again!
• Scrap a lot of money? That makes a big bang
• A grave situation - order second category weapon