The most common and most likely answer to this crossword clue is the 4 letter word GEMS
G
E
M
S
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The straight part
We know that "stones" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stones = gems.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 GEMS mean?
GEMS noun- A precious stone, usually of substantial monetary value or prized for its beauty or shine.
- Any precious or highly valued thing or person.
- Anything of small size, or expressed within brief limits, which is regarded as a gem on account of its beauty or value, such as a small picture, a verse of poetry, or an epigram.
- A gemma or leaf-bud.
- A type of geometrid moth, Orthonama obstipata.
- A package containing programs or libraries for the Ruby programming language.
- A size of type between brilliant (4-point) and diamond (4½-point), running 222 lines to the foot.
- To adorn with, or as if with, gems.