Piece of paving (4)
I believe the answer is:
slab
'piece of paving' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for slab that I've seen before include "Thick piece of something" , "Flat broad piece as of stone" , "Broad, thick piece of wood, stone" , "Paving stone" , "Piece, e.g. of cake" .)