One's best pen friend? (8)
I believe the answer is:
sheepdog
This could be a double definition.
'one's best' is the first definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'pen friend?' is the second definition.
The answer and definition can be both animals as well as being singular nouns.
Maybe they are linked in a way I don't understand?
Can you help me to learn more?
(Other definitions for sheepdog that I've seen before include "Canine trained to control flock" , "Farmer's herding helper" , "Shaggy-haired canine" , "Working farm animal" , "Collie, perhaps" .)