Being fishy, possibly hard to eat (3)
I believe the answer is:
roe
'being' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for roe that I've seen before include "Fish eggs; small deer" , "A mass of fish-eggs" , "Swift runner" , "Part of fish, sounds like go through water" , "Caviar" .)