Citizen Kane writer's marriage announced from northern city (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Homophone/pun/aural wordplay [ announced ] of MANK UNION ("Citizen Kane writer's marriage") The screenplay of Citizen Kane was written by Orson Wells and Herman J Mankiewicz (aka Mank), played by Gary Oldman in a 2020 movie called Mank .