Beam of sunlight (3)
I believe the answer is:
ray
'beam of sunlight' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ray that I've seen before include "Column of light on the fish?" , "beamer?" , "Flat fish or sun beam" , "Shaft of light" , "Second note for the flat fish" .)