There's nothing in the roll but chicken (7)
I believe the answer is:
rooster
'chicken' is the definition.
(I know that rooster is a type of chicken)
'there's nothing in the roll' is the wordplay.
'there's nothing' becomes 'o' (I've seen this in other clues).
'in the' indicates putting letters inside.
'roll' becomes 'roster' (roll can mean a list or roster).
'o' inserted within 'roster' is 'ROOSTER'.
'but' acts as a link.
(Other definitions for rooster that I've seen before include "Farmyard fowl" , "Morning caller" , "Domestic cock" , "Bird that wakes up" , "Chanticleer" .)