Obedient former pupil getting domestic (9)
I believe the answer is:
observant
'obedient' is the definition.
(thesaurus)
'former pupil getting domestic' is the wordplay.
'former pupil' becomes 'OB' (abbreviation for 'Old Boy').
'getting' says to put letters next to each other.
'domestic' becomes 'servant' (I've seen this before).
'ob'+'servant'='OBSERVANT'
(Other definitions for observant that I've seen before include "Watchful" , "Quick to notice things" , "diligent in duty" , "keeping close eye on things" , "with a keen eye" .)