Cock and duck appearing in list (7)
I believe the answer is:
rooster
'cock' is the definition.
('rooster' can be a synonym of 'cock')
'duck appearing in list' is the wordplay.
'duck appearing' becomes 'o' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' is an insertion indicator.
'list' becomes 'roster' (roster is a kind of list).
'o' inserted inside 'roster' is 'ROOSTER'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for rooster that I've seen before include "Early-morning caller" , "Adult male chicken" , "Domestic cock" , "Male domestic fowl in USA" , "Bird that wakes up" .)