The most common and most likely answer to this crossword clue is the 3 letter word ALT
I've seen this crossword clue in The Guardian
A
L
T
More clues leading to the result ALT
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 = alt.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 ALT mean?
ALT noun- High pitch, of a voice or instrument; especially, the octave above the top line of the treble stave.
- A state of excitement, a heightened emotional condition.
- An alternate or secondary character.
- An alternate account.
- An alternative investment or alternative fund.
- Happening by turns; one following the other in succession of time or place; first one and then the other (repeatedly)
- Designating the members in a series, which regularly intervene between the members of another series, as the odd or even numbers of the numerals; every other; every second.
- Other; alternative.
- (of leaves) Distributed singly at different heights of the stem, and at equal intervals as respects angular divergence.
- Relating to a choice between two or more possibilities.
- Other; different from something else.
- Not traditional, outside the mainstream, underground.
- Alternate, reciprocal.
- The absolute height of a location, usually measured from sea level.
- A vertical distance.
- The distance measured perpendicularly from a figure's vertex to the opposite side of the vertex.
- The angular distance of a heavenly body above our Earth's horizon.
- Height of rank or excellence; superiority.
- (in the plural) Elevation of spirits; heroics; haughty airs.
- Highest point or degree.