Elizabeth's favourite duck (5)
I believe the answer is:
drake
This could be a double definition.
'elizabeth's favourite' is the first definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'duck' is the second definition.
(drake is a male duck)
Can you help me to learn more?
(Other definitions for drake that I've seen before include "Captain of the Golden Hind, d. 1596" , "Plymouth bowler" , "Elizabethan sailor" , "Seaman" , "English circumnavigator, d. 1596" .)