A pebble on the beach? (9)
I believe the answer is:
sandstone
'a pebble on the beach?' is the definition.
I can't judge whether this defines the answer.
'pebble on the beach?' is the wordplay.
'pebble' becomes 'stone' (I've seen this in another clue).
'on' means one lot of letters go next to another.
'the beach?' becomes 'sand'.
'stone' put after 'sand' is 'SANDSTONE'.
Can you help me to learn more?
(Other definitions for sandstone that I've seen before include "Type of sedimentary rock" , "Among the best of building materials" , "Such building material" , "Rock containing quartz grains" .)