Youngsters producing rubbish (6)

I believe the answer is:

litter

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'rubbish' is the definition.
(litter is a kind of rubbish)

I don't understand the remainder of the clue.

(Other definitions for litter that I've seen before include "Light bed - rubbish" , "waste material" , "little ones?" , "Number of animals born to the same mother at the same time" , "Do the kittens create rubbish?" .)

I've seen this clue in The Guardian.

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