One’s best pen friend? (8)
I believe the answer is:
sheepdog
This might be a double definition.
'one's best' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'pen friend?' is the second definition.
The answer and definition can be both animals as well as being singular nouns.
Perhaps there's a link between them 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" .)