The most common and most likely answer to this crossword clue is the 2 plus 3 plus 7 letter word DO NOT DISTURB
I've seen this crossword clue in The Guardian
D
O
N
O
T
D
I
S
T
U
R
B
More clues leading to the result DO NOT DISTURB
Buddy explains!

The straight part
We know that "Leave me alone" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leave me alone = do not disturb.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.