Some fishes are female (3)
I believe the answer is:
she
'are female' is the definition.
(I've seen this before)
'some fishes' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'SHE' can be found hidden inside 'fishes'.
(Other definitions for she that I've seen before include "Rider's novel" , "Female pronoun" , "1887 Rider Haggard novel" , "That woman" , "The one who must be obeyed" .)