What a setter, or anyone antisocial, may drop (6)
I believe the answer is:
litter
'drop' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for litter that I've seen before include "Do the kittens create rubbish?" , "dropped by a new dam, perhaps?" , "Light bed - rubbish" , "Offspring of a multiple birth" , "Clean up the canine offspring?" .)