Kittens' rubbish (6)
I believe the answer is:
litter
I believe this clue is a double definition.
'kittens'' is the first definition.
(I've seen this before)
'rubbish' is the second definition.
(litter is a kind of rubbish)
(Other definitions for litter that I've seen before include "cats go here" , "dropped by a new dam, perhaps?" , "Rubbish - baby animals" , "Untidy refuse for animal young" , "Not a neat" .)