Sci-fi weapon? (5)
I believe the answer is:
laser
'sci-fi weapon?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for laser that I've seen before include "Intense light generator" , "Device producing a narrow, intense beam of light" , "scientific device" , "Device producing thin beam of light" , "Coherent light beam" .)