The most common and most likely answer to this crossword clue is the 9 letter word SANDSTONE
I've seen this crossword clue in The Sunday Telegraph
S
A
N
D
S
T
O
N
E
More clues leading to the result SANDSTONE
- Way a person goes about with first bit of Southend rock
- Oddly, Spain doesn’t fancy the Rock
- Sun tan’s done when oiled in ancient section of beach?
- Building material makes smoother sound
- Rock succeeded with singular quality
- Building material carried by thousands to neighbourhood
- French novelist’s sound rock
- Smooth bit of stuff, tenor’s 16?
- Ann tossed broken rock
- Sulfur and a bit of slime ring sedimentary formation
Buddy explains!

The straight part
We know that "rock" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rock = sandstone.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SANDSTONE mean?
SANDSTONE noun- A sedimentary rock produced by the consolidation and compaction of sand, cemented with clay etc.