### Clue: Muted sound when treacherous fascist backed (3-3)
### Answer: WAH-WAH 
 ### Explanation: Definition: Muted sound
 **Reversal of**(… backed) HAW-HAW(Lord, nickname of various persons broadcasting fascist/Nazi propaganda to the UK from Germany during WW2).
Defn: … produced on musical instruments – eg. on brass instruments by alternatively applying and removing a mute