Roll containing old chicken (7)
I believe the answer is:
rooster
'chicken' is the definition.
(I know that rooster is a type of chicken)
'roll containing old' is the wordplay.
I cannot quite see how this works, but
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is present in the answer.
'roll' could be 'roster' (roll can mean a list or roster) and 'roster' is located in the leftover letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rooster that I've seen before include "American cockerel" , "Male hen" , "one going to sleep" , "American cock" , "male with comb" .)