The most common and most likely answer to this crossword clue is the 9 letter word HEADCOUNT
I've seen this crossword clue in The Guardian
H
E
A
D
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Buddy explains!
The straight part
We know that "People on staff" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case people on staff = headcount.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 HEADCOUNT mean?
HEADCOUNT noun- The act of counting how many people are present in a group.
- The number of people present in a group or employed by a company.
- More generally, a consideration of a company's appropriate staffing level based on some larger context. (Generally used adjectivally.)
- By extension, one slot in a workgroup, filled or to be filled by one person.