Rock star's first and second sound (9)
I believe the answer is:
sandstone
'rock' is the definition.
(I know that sandstone is a type of arenaceous rock)
'star's first and second sound' is the wordplay.
'star's first' becomes 's' (tst letter of 'star').
'second' becomes 's' (common abbreviation).
'sound' becomes 'tone' (tone is a kind of sound).
's'+'and'+'s'+'tone'='SANDSTONE'
(Other definitions for sandstone that I've seen before include "Among the best of building materials" , "Rock containing quartz grains" , "Such building material" , "Type of sedimentary rock" .)