Stu tried to remove debris (8)
I believe the answer is:
detritus
'debris' is the definition.
('detritus' can be a synonym of 'debris')
'stu tried to remove' is the wordplay.
'to remove' is an anagram indicator (move the letters again).
'stu'+'tried'='stutried'
'stutried' anagrammed gives 'DETRITUS'.
(Other definitions for detritus that I've seen before include "Waste, debris" , "It rusted to become debris" , "Worn down rocks, gravel etc." , "Accumulated fragments from erosion - it rusted (anag)" , "Refuse" .)