The most common and most likely answer to this crossword clue is the 4 plus 3 letter word FALL OUT
I've seen this crossword clue in The Times
F
A
L
L
O
U
T
More clues leading to the result FALL OUT
Buddy explains!
The straight part
We know that "Happen/to disagree" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case happen/to disagree = fall out.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 FALL OUT mean?
FALL OUT noun- The event of small airborne particles falling to the ground in significant quantities as a result of major industrial activity, volcano eruption, sandstorm, nuclear explosion, etc.
- The particles themselves.
- A negative side effect; an undesirable or unexpected consequence.
- A declined offer in a sales transaction when acceptance was presumed.
- The person who declines such an offer.
- An impromptu guest used to fill in for another guest spot who is a no show or who has cancelled last minute