The most common and most likely answer to this crossword clue is the 5 letter word JEWEL
I've seen this crossword clue in The Guardian
J
E
W
E
L
More clues leading to the result JEWEL
- Brilliant wool supplier fills empty jail
- Sheep penned within limits of jail is highly rated
- Prize baguette?
- Brilliant combination of the Hebrew and the Spanish
- . Shining example in tale we joke about
- Ultimately, he saw the deal — Jack is first, possibly a diamond
- In France I get discontented wife large gemstone
- Jack left after pocketing fantastic wee gem
Buddy explains!

The straight part
We know that "gemstone" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gemstone = jewel.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 JEWEL mean?
JEWEL noun- A precious or semi-precious stone; gem, gemstone.
- A valuable object used for personal ornamentation, especially one made of precious metals and stones; a piece of jewellery.
- Anything precious or valuable.
- A bearing for a pivot in a watch, formed of a crystal or precious stone.
- Any of various lycaenid butterflies of the genus Hypochrysops.
- The clitoris.
- To bejewel; to decorate or bedeck with jewels or gems.