Famous study acquired by the Queen is sent back (8)
I believe the answer is:
renowned
'famous' is the definition.
(I know that famous can be written as renowned)
'study acquired by the queen is sent back' is the wordplay.
'study' becomes 'den' (term for a study or office).
'acquired' becomes 'won' (I've seen this in another clue).
'by' means one lot of letters go next to another.
'the queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'is sent back' says the letters should be written backwards.
'den'+'won'+'er'='denwoner'
'denwoner' backwards is 'RENOWNED'.
(Other definitions for renowned that I've seen before include "Illustrious" , "Famed" , "Widely respected" , "Prominent" , "Widely known and esteemed" .)