A roll containing nothing but chicken (7)
I believe the answer is:
rooster
'chicken' is the definition.
(I know that rooster is a type of chicken)
'a roll containing nothing' is the wordplay.
'a roll' becomes 'roster' (roll can mean a list or roster).
'containing' means one lot of letters goes inside another.
'nothing' becomes 'O' (looks like zero - 0).
'roster' placed around 'o' is 'ROOSTER'.
'but' is the link.
(Other definitions for rooster that I've seen before include "Cockerel (mainly US)" , "male with comb" , "Male domestic fowl in USA" , "Farmyard bird" , "Early-morning caller" .)