Criticise material used for roofing (5)
I believe the answer is:
slate
I believe this clue is a double definition.
'criticise' is the first definition.
(I've seen this before)
'material used for roofing' is the second definition.
(slate is used on roofs)
(Other definitions for slate that I've seen before include "Stone used for roofing" , "Roofing tile" , "Roofing plate" , "Grey stone; tab" , "rock used in building" .)