Therapist's in work, at hospital (9)
I believe the answer is:
homeopath
'therapist's' is the definition.
(thesaurus)
'in work at hospital' is the wordplay.
'in' becomes 'home' ('he's in' can mean 'he's home'**).
'work' becomes 'op' (abbreviation for opus).
'hospital' becomes 'h'.
'home'+'op'+'at'+'h'='HOMEOPATH'
(Other definitions for homeopath that I've seen before include "Quack perhaps" , "Health practitioner" , "Alternative practitioner" , "he treats you, naturally" , "therapist" .)