The most common and most likely answer to this crossword clue is the 6 letter word LANCET
I've seen this crossword clue in The Daily Telegraph
L
A
N
C
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T
More clues leading to the result LANCET
- Window that opens in theatre
- Awfully clean on top of table, surgeon’s knife
- Narrow window for research publication
- Knight disposing of leftover blade
- Medical journal allowed to include an opening for chiropractor
- Window opener in hospital
- Operator’s instrument in window
- Window that’s needed for theatre opening
- Line worker put around church window
- Point employed by orderly number broaching secure unit’s closure
Buddy explains!

The straight part
We know that "window" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case window = lancet.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 LANCET mean?
LANCET noun- A sharp, pointed, two-edged surgical instrument used in venesection and for opening abscesses etc.
- A small, sterile single-use needle used to draw a drop of blood for testing, as with a glucometer.
- An iron bar used for tapping a melting furnace.
- A high narrow window, terminating in an arch acutely pointed, often double or triple, common in the first half of the 13th century.
- To pierce with a lancet.