Devotee training, but not at home (8)
I believe the answer is:
disciple
'devotee' is the definition.
(thesaurus)
'training but not at home' is the wordplay.
'training' becomes 'discipline' (discipline is a kind of training).
'but not' suggests deleting specific letters.
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'discipline' with 'in' taken away is 'DISCIPLE'.
(Other definitions for disciple that I've seen before include "Learner in school" , "Christian?" , "Personal follower of Christ" , "one believes" , "Follower of a religious leader" .)