Chunk of concrete (4)
I believe the answer is:
slab
'chunk of concrete' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slab that I've seen before include "Broad, thick piece of wood, stone" , "Piece of paving" , "Paving stone" , "Chunk of wood" , "Mortuary table" .)