Nothing inside about eggs (3)
I believe the answer is:
roe
'eggs' is the definition.
(fish eggs)
'nothing inside about' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'inside' is an insertion indicator.
'about' becomes 're' ('re' means regarding or about).
'o' placed into 're' is 'ROE'.
(Other definitions for roe that I've seen before include "If hard, eggs" , "Part of fish, sounds like go through water" , "Caviar" , "Mass of fish eggs" , "Food from fish" .)