The most common and most likely answer to this crossword clue is the 9 letter word TRILOBITE
I've seen this crossword clue in Independent
T
R
I
L
O
B
I
T
E
More clues leading to the result TRILOBITE
- Fossil — see black one with dull exterior
- I chuck in worn-out fossil
- Fossil – see black one with dull exterior
- Libretto I rewrote for one in rock
- Old fragment obtained by tiler when working is a fossil
- Ingesting tail of pterodactyl, three taste a fossilised arthropod
- Bitter oil roused ancient creature
- Fossil of worm, one with well-worn exterior
- Finally felt upset about obituary for old fossil
- Fossil I behold with black, dull exterior
Buddy explains!
The straight part
We know that "one in rock" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one in rock = trilobite.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 TRILOBITE mean?
TRILOBITE noun- An extinct arthropod of the class Trilobita, whose body had three large lobes.