Nuclear (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nuclear</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for atomic that I've seen before include "Sort of bomb, number, or power" , "Relating to the smallest component of an element" , "Extremely minute" , "I'm Cato (anag.)" , "Realting to nuclear energy" .)
(Other definitions for reactor that I've seen before include "chemical substance!" , "Nuclear energy source" , "device that's energy-producing" , "nuclear facility" , "power supplier" .)