Flat-bodied fish (3)
I believe the answer is:
ray
'flat-bodied fish' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ray that I've seen before include "Gleam" , "may be electric" , "Flatfish or sunbeam" , "Sunbeam or flat fish" , "Column of light on the fish?" .)