Starfish arm (3)
I believe the answer is:
ray
'starfish arm' 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 "Second note for the flat fish" , "Beam - skate" , "Flat fish or sun beam" , "Man who engaged in surrealist photography" , "Gleam" .)