The most common and most likely answer to this crossword clue is the 5 letter word QUAKE
I've seen this crossword clue in The Times
Q
U
A
K
E
Buddy explains!

The straight part
We know that "Major disturbance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case major disturbance = quake.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 QUAKE mean?
QUAKE noun- A trembling or shaking.
- An earthquake, a trembling of the ground with force.
- To tremble or shake.
- To be in a state of fear, shock, amazement, etc., such as might cause one to tremble.