Accumulated debris (8)
I believe the answer is:
detritus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">accumulated debris</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for detritus that I've seen before include "Accumulation of debris - it rusted (anag)" , "Rubbish - it rusted (anag)" , "Gravel or loose matter produced by erosion" , "Loose eroded matter" , "Worn down rocks, gravel etc." .)