Swimmer's hero! (7)
I believe the answer is:
herring
This clue could be a double definition.
'swimmer's' is the first definition.
(herring is a type of fish)
'hero' is the second definition.
The definition and answer can be both things that one consumes for nourishment as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
Can you help me to learn more?
(Other definitions for herring that I've seen before include "Saltwater fish" , "Sea fish" , "Fatty fish" , "one could be soused" , "It's certainly fishy!" .)