The most common and most likely answer to this crossword clue is the 9 letter word BEEKEEPER
I've seen this crossword clue in The Guardian
B
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K
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More clues leading to the result BEEKEEPER
- Yikes, buzzer has caught its owner?
- In alarm, perhaps, I’m shocked, as protector of the workers?
- Overseer of colony‘s alarmed cry, breaking pager
- Spooner’s important pager, one working with constant buzz?
- 23 accepts alarm call from one working in the colonies
- One who deals with a hive of activity
- Guardian of the workers?
- Retain queen after worker for man with a skep
- Squeal with alarm about one exploiting workers
- Opener's pager given by Spooner to apiarist
Buddy explains!

The straight part
We know that "Overseer of colony" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case overseer of colony = beekeeper.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 BEEKEEPER mean?
BEEKEEPER noun- A person who maintains hives and keeps bees, especially for the production of honey.