Leave awful smears on the material (8)
I believe the answer is:
gossamer
'the material' is the definition.
(gossamer is a kind of material)
'leave awful smears on' is the wordplay.
'leave' becomes 'go' (**).
'awful' is an anagram indicator.
'on' means one lot of letters goes inside another (as in clothing \'on\' a person).
'smears' with letters rearranged gives 'ssamer'.
'go' going within 'ssamer' is 'GOSSAMER'.
(Other definitions for gossamer that I've seen before include "Filmy floating cobweb" , "Very fine, insubstantial" , "Filmy cobweb - very fine fabric" , "Fine product of spiders" , "Fine spider's silk" .)