Usher set off to part of hospital (7)
I believe the answer is:
steward
'usher' is the definition.
(thesaurus)
'set off to part of hospital' is the wordplay.
'off' indicates anagramming the letters.
'to part of hospital' becomes 'ward' ('ward' is part of 'hospital').
'set' anagrammed gives 'ste'.
'ste'+'ward'='STEWARD'
(Other definitions for steward that I've seen before include "Flight attendant" , "Attendant -- wed star (anag)" , "Racing official" , "Caretaker" , "Crew member" .)