Trumpets opinions, well-argued, very, very loudly (6,3)

I believe the answer is:

sounds off

'trumpets opinions' is the definition.
(to sound off is to give one's opinions)

'well-argued very very loudly' is the wordplay.
'well-argued' becomes 'sound' (sound can mean valid or well-founded).
'very' becomes 'so' (both can mean 'extremely').
'very loudly' becomes 'ff' (short for fortissimo, 'very loud' in music).
'sound'+'so'+'ff'='SOUNDS OFF'

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app