Little sibling digesting Authorised Version? Well done! (5)
I believe the answer is:
bravo
'well done' is the definition.
(bravo is used to express admiration)
'little sibling digesting authorised version?' is the wordplay.
'little sibling' becomes 'bro' (short for 'brother').
'digesting' means one lot of letters goes inside another (inserted letters are eaten or ingested).
'authorised version?' becomes 'AV' (authorised version of the Bible).
'bro' placed around 'av' is 'BRAVO'.
(Other definitions for bravo that I've seen before include "A cry meaning well done" , "Hurrah!" , "Exclamation of approval" , "Thug, hired assassin; B (in radio communication)" , "bully" .)