Study in advanced English (3)
I believe the answer is:
den
'study' is the definition.
(term for a study or office)
'in advanced english' is the wordplay.
'in' indicates the answer is hidden within the clue.
'DEN' can be found hidden inside 'advanced english'.
(Other definitions for den that I've seen before include "Cave" , "Animal's lair or man's study" , "Animal's home or gent's study" , "Animal habitation" , "Private office" .)