The term 'Kind of Clock or Bomb' can be summarized by two crossword solutions: ATOMIC (6 letters) and TIME (4 letters). An ATOMIC clock is a type of clock that uses the frequency of an electron transition in an atom to measure TIME. ATOMIC clocks are the most accurate clocks available and are used to set international standards for TIME. A TIME bomb is a device that is set to explode at a certain TIME, usually as part of an act of sabotage or terrorism.