mouthpiece
n.a person or organization that speaks for someone else. It can also mean the part of a musical instrument that you blow into.
n.a person, newspaper, or organization that expresses the views of another; also, the part of a wind instrument or telephone placed in or near the mouth.
“The newspaper acts as a mouthpiece for the government.”
“The lawyer served as a mouthpiece for the corporation, delivering their official statement to the waiting reporters.”
“While the trumpet's mouthpiece is essential for sound production, the term is more frequently used in political science to describe media outlets that lack editorial independence from their sponsors.”
Often used with the preposition 'for' when referring to a person or organization.
“President Trump’s outgoing press secretary, who had been a key mouthpiece for the administration since the start of Trump’s second term, addressed reporters for perhaps the last time earlier today.”
From mouth + piece.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.