Small pen, coffin nail and mesh (articulated) (6)
I believe the answer is:
cygnet
'small pen' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Maybe there's a link between them I don't understand?
'coffin nail and mesh articulated' is the wordplay.
I cannot quite see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is found in the answer.
'nail' could be 'get' (both can mean to apprehend) and 'get' is present in the remaining letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for cygnet that I've seen before include "Sounds like the type of ring" , "Aquatic creature" , "Young swan" , "that's no ugly duckling" , "one seen swimming near pen" .)