French novelist's sound rock (9)
I believe the answer is:
sandstone
'rock' is the definition.
(I know that sandstone is a type of arenaceous rock)
'french novelist's sound' is the wordplay.
'french novelist's' becomes 'sand's' (George Sand 1804-1876).
'sound' becomes 'tone' (tone is a kind of sound).
'sands'+'tone'='SANDSTONE'
(Other definitions for sandstone that I've seen before include "Such building material" , "Rock containing quartz grains" , "Among the best of building materials" , "Type of sedimentary rock" .)