The most common and most likely answer to this crossword clue is the 8 letter word VAULTING
I've seen this crossword clue in The Guardian
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Buddy explains!
The straight part
We know that "Going over/stonework in medieval roof, perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case going over/stonework in medieval roof, perhaps = vaulting.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 VAULTING mean?
VAULTING verb- To build as, or cover with a vault.
- To jump or leap over.
- The practice of constructing vaults, or a particular method of such construction.
- A vaulted structure; such structures treated as a group.
- The sport of gymnastics and dance routines performed on horseback, and on the longe line.
- Leaning upward or over
- Exaggerated or overreaching
- Performing