The most common and most likely answer to this crossword clue is the 8 letter word GEMSTONE
I've seen this crossword clue in The Guardian
G
E
M
S
T
O
N
E
More clues leading to the result GEMSTONE
- Rock 'em, interrupting G&S air
- Key European manuscript with character is a precious jewel
- Admirable people pitch for baguette
- Sparkler – one gets used around the 5th of November
- Receive absorbing manuscript, a cameo?
- Gets excited with single accepting male’s jewel
- Some gent renovated jewel
- Stem broken and missing case that’s precious
- Gnome set out to find precious rock
- Ruby and Meg rejected — put on weight
Buddy explains!

The straight part
We know that "precious rock" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case precious rock = gemstone.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 GEMSTONE mean?
GEMSTONE noun- A gem, usually made of minerals.