The most common and most likely answer to this crossword clue is the 6 letter word DELETE
I've seen this crossword clue in Independent
D
E
L
E
T
E
More clues leading to the result DELETE
Buddy explains!

The straight part
We know that "Key" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case key = delete.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 DELETE mean?
DELETE noun- A key that may be pressed to delete something (such as text or files) from a computer.
- A deletion.
- (recorded entertainment industry) A remainder of a music or video release.
- To remove, get rid of or erase, especially written or printed material, or data on a computer or other device.