Evaluate following material, but slash (8)
I believe the answer is:
lacerate
'slash' is the definition.
(I've seen this before)
'evaluate following material' is the wordplay.
'evaluate' becomes 'rate' (rating is a kind of evaluating).
'following' is a charade indicator (letters next to each other).
'material' becomes 'lace' (lace is a kind of material).
'rate' put after 'lace' is 'LACERATE'.
'but' acts as a link.
(Other definitions for lacerate that I've seen before include "Injure be tearing, wound roughly" , "Harrow" , "Slash" , "Tear roughly, cut jaggedly" , "Tear or gash roughly" .)