Strongly criticises the roof tiles? (6)
I believe the answer is:
slates
'strongly criticises the roof tiles?' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for slates that I've seen before include "Abuses with roof tiles?" , "Strongly criticises the roof tiles" , "Thin layers of rock for roofing" , "Criticises severely using roof coverings" , "Berates with roofing tiles" .)