Following her criticism of his extra-marital affairs, Clarke's father turned her out of the house and cut off her funds. She had to leave the Royal College in 1910 and supported herself through her viola playing. Clarke became one of the first female professional orchestral musicians when she was selected by Sir Henry Wood to play in the Queen's Hall Orchestra in 1912. In 1916 she moved to the United States to continue her performing career. A short, lyrical piece for viola and piano entitled "Morpheus", composed under the pseudonym of "Anthony Trent", was premiered at her 1918 joint recital with cellist May Mukle in New York City. Reviewers praised the "Trent", largely ignoring the works credited to Clarke premiered in the same recital. Her compositional career peaked in a brief period, beginning with the viola sonata she entered in a 1919 competition sponsored by Elizabeth Sprague Coolidge, Clarke's neighbour and a patron of the arts.