Is his office a 'booking' one? (7)

I believe the answer is:

referee

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

'is his office a booking one?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.

This is all the clue.

Can you help me to learn more?

(Other definitions for referee that I've seen before include "Arbiter" , "Game official" , "One who decides" , "Umpire; arbitrator" , "Sporting arbitrator" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app