List includes old farm animal (7)
I believe the answer is:
rooster
'farm animal' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Maybe there's a link between them I don't understand?
'list includes old' is the wordplay.
'list' becomes 'roster' (a roster is a list or register).
'includes' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'roster' placed around 'o' is 'ROOSTER'.
Can you help me to learn more?
(Other definitions for rooster that I've seen before include "Adult male domestic fowl" , "Farmyard cock" , "one going to sleep" , "Morning caller" , "Crowing bird" .)