The most common and most likely answer to this crossword clue is the 9 letter word OVERSIGHT
I've seen this crossword clue in The Guardian
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More clues leading to the result OVERSIGHT
- Mistake in supervision
- Innocent mistake concerning vision
- Error in commentator's position on left
- Give short change in error
- Slip-up on particular area in speech
- 8 Give short-tempered supervision
- Supervision error
- Supervision or lack of supervision
- Concerned with anything that is seen as supervision
- Management blunder created complete spectacle
Buddy explains!

The straight part
We know that "Slip-up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case slip-up = oversight.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 OVERSIGHT mean?
OVERSIGHT noun- An omission; something that is left out, missed or forgotten.
- Supervision or management.
- Overview
- To oversee; to supervise.
- (Wiktionary and WMF jargon) To suppress content in a way that removes or minimizes its visibility or viewability.