The most common and most likely answer to this crossword clue is the 4 letter word OOPS
I've seen this crossword clue in The Times
O
O
P
S
More clues leading to the result OOPS
- It’s my fault henhouses won’t open
- No prime Co-ops cry over spilt milk?
- I've messed up zero operations
- Rings after husband leaves? Oh dear!
- It is my fault old soprano hampers work
- . Top removed from prison cells? That’s an error
- Silly me loves writing puzzles after vacation!
- I blundered, needing ultimately to go up backwards
- Ghost briefly makes a comeback; sorry about that
- I’ve messed up in no surgical procedures!
Buddy explains!

The straight part
We know that "It is my fault" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it is my fault = oops.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 OOPS mean?
OOPS noun- A minor mistake or unforseen difficulty.
- To make a mistake; to blunder.
- Acknowledging a mistake.