Extremely canny gentlemen edit what's produced by pen (6)
I believe the answer is:
cygnet
'pen' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for cygnet that I've seen before include "Young swan" , "Young water bird" , "Immature swan" , "Small pen, perhaps?" , "small pen? Possibly" .)