Patriotic song, Arne air Butlin's broadcast (4,9)
I believe the answer is:
rule britannia
'patriotic song' is the definition.
(I've seen this before)
'arne air butlin's broadcast' is the wordplay.
'broadcast' is an anagram indicator.
'arne'+'air'+'butlin'='arneairbutlin'
'arneairbutlin' anagrammed gives 'RULE BRITANNIA'.
(Other definitions for rule britannia that I've seen before include "Arne's patriotic song" , "Arne patriotic song" , "Thomas Arne's patriotic composition" , "Britons never slaves song" , "Patriotic air" .)