Simpson losing head in drinking spree? He may be a facilitator (9)
I believe the answer is:
bartender
'he may be a facilitator' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'simpson losing head in drinking spree?' is the wordplay.
'simpson' becomes 'Bart' (Bart Simpson, The Simpsons character).
'losing head' means to remove the first letter.
'in' means one lot of letters goes inside another.
'drinking spree?' becomes 'bender' (bender can mean a night of drinking).
'bart' with its first letter taken off is 'art'.
'art' put inside 'bender' is 'BARTENDER'.
(Other definitions for bartender that I've seen before include "local employee" , "Server in pub" , "Liquor salesman" , "Pub worker" , "Landlord perhaps" .)