Zap in the microwave (4)
I believe the answer is:
nuke
'zap in the microwave' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nuke that I've seen before include "Destroy with a very powerful 18" , "Nuclear weapon (sl.)" , "Attack with H-bomb (slang abbr.)" , "Drop huge bomb on" , "Attack with an atomic weapon" .)