Number of employees possibly quartered (5)

I believe the answer is:

staff

I'm a little stuck... Click here to teach me more about this clue!

'number of employees' is the definition.
'staff' can be an answer for 'employees' (I've seen this in other clues). I'm not sure about the 'number of' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for staff that I've seen before include "Employees; sign of office" , "Administrators etc - stick" , "Rod; workers" , "Walking-stick" , "See 11" .)

I've seen this clue in the Evening Standard.

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