The most common and most likely answer to this crossword clue is the 9 letter word CUNEIFORM
I've seen this crossword clue in The Guardian
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Buddy explains!

The straight part
We know that "wedge-shaped" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wedge-shaped = cuneiform.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 CUNEIFORM mean?
CUNEIFORM noun- An ancient Mesopotamian writing system, adapted within several language families, originating as pictograms in Sumer around the 30th century BC, evolving into more abstract and characteristic wedge shapes formed by a blunt reed stylus on clay tablets.
- A wedge-shaped bone, especially a cuneiform bone.
- Having the form of a wedge; wedge-shaped, especially with a tapered end.
- Written in the cuneiform writing system.