Recalled part of Wagnerian opera being broadcast (2,3)
I believe the answer is:
on air
'being broadcast' is the definition.
(on air on radio or TV)
'recalled part of wagnerian opera' is the wordplay.
'recalled' is a reversal indicator.
'part of' says the answer is hidden in the clue.
'riano' is hidden within 'wagnerian opera'.
'riano' in reverse letter order is 'ON-AIR'.
(Other definitions for on air that I've seen before include "Cushioned" , "Broadcasting at this moment" , "Transmitting now!" , "In the act of broadcasting" , "Currently broadcasting" .)