The phrase "a senior one" is correct and usable in written English.
It can be used to refer to a person or position that is of a higher rank or level, often in a professional context.
Example: "In our department, we have a junior analyst and a senior one who oversees the team's projects."
Alternatives: "a higher-level one" or "a more experienced one."
Hicks may not have had any political experience, but her job in the campaign was a senior one from the start.
Between them, they have four degrees; she is an experienced midwife in her mid-40s; Paul, a few years older, is a manager – a senior one – and also in the public sector.
"The truth of the matter is, if the inquiry was going to express a view with any kind of authority on the question of legality, it would need a legal member and quite a senior one," the judge said.
Almost all appointments or promotions being decided within the system, a junior judge does not lightly refuse a favour to a senior one.
As Joel Mosbacher raised his own family and advanced in his rabbinical career, moving from an assistant's position outside Atlanta to a senior one in this New Jersey suburb, he recognized that no prayer, no fast, no act of religious charity could give him what he wanted.
The post was a senior one for a captain; Robert Goldthwaite had held the post while he was a rear admiral.
#reshuffle October 7, 2013 Desmond Swayne was already a whip, but now he is a more senior one.
When I was a college senior, one of my biggest concerns about the recession I was graduating into was that I would not be able to afford to live on my own.
One is a senior biostatistician, one is an expert in surgical RCTs and one is an expert in medical RCTs.
Dr Emma Weitkamp, of the University of the West of England, is a senior lecturer on one of the newer programmes.
On the return trip, Albert An, 17, a senior, was one of five riders.
