He's brainy, using no bin! (3)
I believe the answer is:
ray
'he's' is the definition.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for ray that I've seen before include "Column of light on the fish?" , "Narrow beam of light" , "A bright beam or flat fish" , "Lindwall" , "A little light" .)