Pave with stones and waterproofing material (5)
I believe the answer is:
pitch
'waterproofing material' is the definition.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for pitch that I've seen before include "cast?" , "-- and putt" , "Throw or fall headlong" , "Level of sound" , "Tar; lob" .)