The most common and most likely answer to this crossword clue is the 6 letter word BETIDE
I've seen this crossword clue in Independent
B
E
T
I
D
E
More clues leading to the result BETIDE
Buddy explains!
The straight part
We know that "Happen to" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case happen to = betide.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 BETIDE mean?
BETIDE verb- To happen unto; to befall.
- To happen; to take place; to bechance or befall.