Bit of roofing (4)
I believe the answer is:
tile
'bit of roofing' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tile that I've seen before include "Small slab of baked clay for covering walls, roofs etc" , "Roofing or flooring item" , "Oblong piece of glazed clay for bathroom wall" , "Flat thin slab of clay, for example" , "Roofing slab" .)