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' is an insertion indicator.
'nothing' becomes 'O' (looks like zero - 0).
're' enclosing '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" .)