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 am not certain of the 'number of' bit.

I don't understand the rest of the clue.

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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