About to have nothing but eggs (3)
I believe the answer is:
roe
'eggs' is the definition.
(fish eggs)
'about to have nothing' is the wordplay.
'about' becomes 're' (regarding).
'to have' means one lot of letters goes inside another.
'nothing' becomes 'O' (looks like zero - 0).
're' going around 'o' is 'ROE'.
'but' acts as a link.
(Other definitions for roe that I've seen before include "Fish eggs; small deer" , "shy animal" , "If hard, eggs" , "Hoofed animal(s)" , "A mass of fish-eggs" .)