Young kittens, perhaps, making a mess (6)
I believe the answer is:
litter
This clue might be a double definition.
'young kittens' is the first definition.
'litter' can be an answer for 'kittens' (I've seen this before). I am unsure of the 'young' bit.
'a mess' is the second definition.
(thesaurus)
'perhaps making' is the link.
Can you help me to learn more?
(Other definitions for litter that I've seen before include "Sow's young" , "Odds and ends of rubbish left lying about" , "Number of animals born to the same mother at the same time" , "Refuse; brood" , "Trash left lying about" .)