Sentence:  Nonetheless, some insect prey take advantage of <WSD>clutter</WSD> by hiding in it. Earless ghost swift moths become “invisible” to echolocating bats by forming mating clusters close (less than half a meter) above vegetation and effectively blending into the <WSD>clutter</WSD> of echoes that the bat receives from the leaves and stems around them. 
Meaning of the word marked with <WSD> tags:  A confused disordered jumble of things.