24 across
Austrian
barman
hiding
half
of
national
treasure
in
9
(10)
Austrian barman hiding half of national treasure in 9 (10)
hints
0
checks
0
hints
The definition is at the end of the clue.
How the clue works
The definition is 9, a cross-reference to 9 across (CAKE) — Battenberg being a type of cake. The wordplay comes from Alban Berg, an "Austrian barman" (a man of musical bars), giving BERG, which is placed around ATTENB, half of national treasure David Attenborough (dropping the "orough"), so BERG hides ATTENB to build B-ATTENB-ERG.