The phrase "a trustee at a" is correct and usable in written English.
It can be used when referring to someone who holds a position of trust or responsibility within an organization or institution.
Example: "She was appointed as a trustee at a local charity organization to help manage their funds and resources."
Alternatives: "a board member of a" or "a fiduciary for a".
They themselves belonged to the John Birch Society, and, in the late sixties, Charles was a trustee at a place called the Freedom School, outside Colorado Springs, which had no black students because, its director explained to the Times, "it might present a housing problem because some of his students are segregationists".
He is a trustee at Andrus on Hudson, a nursing home in Hastings-on-Hudson, N.Y.
Leon Ward is a trustee at Plan UK and an ambassador at Young Charity Trustees.
Her mother is a trustee at the Jewish Family Service of MetroWest, a mental health and social services agency in Florham Park, N.J.
Her mother, G. Barrie Landry, is a trustee at the Mother Caroline Academy and Education Center, a Roman Catholic girls' school in Boston.
He also devoted much time to philanthropic pursuits, becoming a trustee at the Rockefeller Foundation and an adviser to President Bill Clinton's philanthropy.
Her mother was a trustee at Greenwich Academy, a girls' college-preparatory and arts day school in Greenwich, Conn., from which the bride graduated.
Khaldoon Al Mubarak, the chairman of Manchester City, a trustee at New York University and a close adviser to Sheik Mansour, may also become involved, even if he is not shaking hands at City Hall and inspecting potential sites for the stadium.
Anna Fielder, a trustee at Privacy International, a group based in London that supports strong data protection laws, said the existing legal regimes in Europe and much of the world were ill equipped to meet the challenges of protecting personal information.
She has also supported equestrian activities -- her daughter, Paige, is a competitive rider -- served as a trustee at Carnegie Hall, and raised money for Bill Clinton.
