The most common and most likely answer to this crossword clue is the 11 letter word SUPERVISION
I've seen this crossword clue in The Times
S
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More clues leading to the result SUPERVISION
Buddy explains!

The straight part
We know that "Overlooking" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case overlooking = supervision.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 SUPERVISION mean?
SUPERVISION noun- The act or instance of supervising.
- Responsible oversight.
- (Cambridge University) A tutorial session for an individual student or a small group.