Answer: littering

AnswerCrossword Clue
litteringProvide (a horse or other animal) with litter as bedding
litteringLeave (rubbish or a number of objects) lying untidily in a place
litteringFill (a text, history, etc.) with examples of something unpleasant
litteringMake (a place) untidy with rubbish or a large number of objects left lying about
litteringLITTER, to scatter rubbish about