Hard or soft, it's fishy (3)
I believe the answer is:
roe
'it's fishy' is the definition.
(fish eggs)
'hard or soft' is the wordplay.
'hard' indicates anagramming the letters.
'soft' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'or' is an anagram of 'ro'.
'ro'+'e'='ROE'
Can you help me to learn more?
(Other definitions for roe that I've seen before include "If hard, eggs" , "Hoofed animal(s)" , "A mass of fish-eggs" , "Mass of fish's eggs" , "Food from fish" .)