Clive Sansom was educated at the Southgate County School, England, and qualified for the London matriculation certificate in 1926. He worked as clerk and salesman for an ironworks company until 1934. Between 1930 and 1935, he studied speech and drama at the Regent Street Polytechnic and the London Speech Institute, and phonetics at London University in 1936. He joined the London Verse Speaking Choir in 1932, won first prize in the 1934 Oxford Verse-Speaking Festival, and participated in individual and group poetry recitals across Southern England for many years. He edited the Speech Institute's Journal from 1934 to 1949. During this period he wrote poetry, plays and short stories, some of which were published in English periodicals.
In 1937, Sansom married Ruth Large, a Tasmanian teacher studying in London, and was appointed lecturer in Speech Training at the Borough Road Training College and the Franciscan Seminary, Woodfield Green. He also lectured at the Speech Institute and was an examiner in speech and drama for LAMDA. Sansom joined the Society of Friends and spent the duration of the Second World War as a conscientious objector working on farms and in market gardens. After the war, he resumed his work with the Academy and Speech Institute before travelling to Tasmania late in 1949.
Sansom was appointed Supervisor of Speech Education with the Tasmanian Education Department in 1951. In this role he established the Speech Education Centre, designed syllabuses, developed curriculum materials and wrote and presented 'Speaking and Listening' ABC radio broadcasts. He was recognised nationally as an authority on spoken language, was an examiner in Speech and Drama for the AMEB from 1951 to 1965, and chaired the Board's national committee for Speech and Drama for several years from 1960. Sansom retired in 1965 and devoted his time to poetry, freelance scriptwriting, the conservation movement and the Society of Friends.
Sansom's love of the English countryside and concern for its conservation was fostered by writers such as Henry Williamson, Richard Jefferies and Thomas Hardy. James Elroy Flecker and T.S. Eliot stimulated his interest in verse drama. His association with Rodney Bennett led to the publication of a number of classroom texts on speech and drama. His first two collections of poetry, published in England before the War, contain personal lyrics in the Georgian tradition, similar to poems by Edward Thomas, Walter de la Mare and W. H. Davies. Sansom wrote his major works in Tasmania. These include a novel, several anthologies of poetry and prose and his verse dramas The Witnesses, The Cathedral, The World Turned Upside Down and Francis of Assisi. Critics praised these for their imaginative treatment of characters and settings and effective use of a variety of verse forms, particularly the dramatic monologue. Sansom championed the use of rhythm and an appreciation of the sound and texture of words. He claimed that some of the Australian poetry published in the 1970s was 'embryo verse' that lacked imagination and technique. Sansom's writing is notable for its English settings. Only a few works, including the poem 'Tasmanian Scene' and a cantata for children There Is an Island, relate directly to his local environment. In 1975, James McAuley commented that 'in a curious way' Sansom 'has never been a figure in the Australian literary scene' (A Map of Australian Verse). His appointment as Patron of the Tasmanian Wilderness Society in 1980 was a fitting acknowledgement of his commitment to the Tasmanian environment.