Beams — fish (4)
I believe the answer is:
rays
This clue is a double definition.
'beams' is the first definition.
(rays of light)
'fish' is the second definition.
(I've seen this before)
(Other definitions for rays that I've seen before include "we hope to catch occasionally out of the blue?" , "Straight lines extending from a point" , "Sunbeams" , "Narrow beams of light" , "Beams from sun or moon" .)