Untidy little beasts (6)
I believe the answer is:
litter
'untidy little' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for litter that I've seen before include "carrier" , "Light bed - rubbish" , "Carelessly dropped rubbish" , "Brood of young born to an animal" , "Refuse; brood" .)