They employ doorkeepers hospital rejected (5)
I believe the answer is:
users
'they employ' is the definition.
(I've seen this before)
'doorkeepers hospital rejected' is the wordplay.
'doorkeepers' becomes 'ushers' ('usher' can be a synonym of 'doorkeeper').
'hospital' becomes 'h'.
'rejected' suggests deleting specific letters.
'ushers' with 'h' taken out is 'USERS'.
(Other definitions for users that I've seen before include "Drug takers" , "Drug addicts" , "People who take drugs" , "Operators" , "People with a drug habit" .)