The swimmer gives us a beam (3)
I believe the answer is:
ray
I believe this is a double definition.
'the swimmer' is the first definition.
(ray is a kind of fish)
'a beam' is the second definition.
(synonyms)
'gives us' acts as a link.
(Other definitions for ray that I've seen before include "Beam or flatfish" , "Shaft of light" , "Beam of light or flat fish" , "Second note for the flat fish" , "Flash < Movie Player" .)