The most common and most likely answer to this crossword clue is the 5 plus 6 letter word LOOSE CANNON
I've seen this crossword clue in The Times
L
O
O
S
E
C
A
N
N
O
N
More clues leading to the result LOOSE CANNON
Buddy explains!
The straight part
We know that "I'm a threat to all" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case i'm a threat to all = loose cannon.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.