The most common and most likely answer to this crossword clue is the 11 letter word SECRETARIES
I've seen this crossword clue in The Guardian
S
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Buddy explains!
The straight part
We know that "office staff" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case office staff = secretaries.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 SECRETARIES mean?
SECRETARIES noun- Someone entrusted with a secret; a confidant.
- A person who keeps records, takes notes and handles general clerical work.
- (often capitalized) The head of a department of government.
- A managerial or leading position in certain non-profit organizations, such as political parties, trade unions, international organizations.
- A type of desk, secretary desk; a secretaire.
- A secretary bird, a bird of the species Sagittarius serpentarius.
- To serve as a secretary of.