The distraught nurses battle over revelatory announcement (3,6)
I believe the answer is:
hey presto
'revelatory announcement' is the definition.
(phrase used when revealing something)
'the distraught nurses battle over' is the wordplay.
'distraught' indicates anagramming the letters.
'nurses' is an insertion indicator (nurse can mean to hold onto or harbour).
'battle' becomes 'ypres' (Ypres is an example).
'over' becomes 'o' (cricket abbreviation).
'the' with letters rearranged gives 'het'.
'het' enclosing 'ypres' is 'heyprest'.
'heyprest'+'o'='HEY-PRESTO'
(Other definitions for hey presto that I've seen before include "suddenly, as if by magic" , "tricky words?" , "that's the trick" , "Abracadabra" , "with the wave of a magic wand!" .)