This nipper is a loner (6,4)
I believe the answer is:
hermit crab
'this nipper is a loner' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'nipper is a loner' is the wordplay.
I cannot quite understand how this works, but
'nipper' could be 'crab' (I have seen 'Nautical nipper' mean 'crab' so perhaps 'nipper' could also mean 'crab') and 'crab' is located in the answer.
'loner' could be 'hermit' (hermit is a kind of loner) and 'hermit' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hermit crab that I've seen before include "Crustacean - tribe march (anag)" , "Marine squatter" , "Little creature with nippers" , "aquatic creature" , "One wearing cast-offs" .)