A "leader writer" is a person who writes influential articles or editorials on behalf of a newspaper, representing its stance or opinion on important issues. Full definition
6.46 pm: Huhne talks about his time as economics leader writer at the Guardian. (theguardian.com)
Euan McColm is a columnist and leader writer who has held senior editorial positions on The Scotsman, The Daily Record and News of the World. (totalpolitics.com)
It is not hard to add more: Mary was almost certainly a teenager, given what we know of marriage customs of the day; a teenage mother, living with a man who is not the father of her child, homeless and seeking asylum - it's enough to have a Daily Mail leader writer salivating in anticipation! (politics.co.uk)