Born in 1865, Claussen was the son of politician Rasmus Claussen and Hanne Sophie (née Henriksen). He began his studies in 1884 and published his first collection of poetry, Naturbørn, which attracted attention due to its daringness and bold eroticism along the lines of Emil Aarestrup's work. For a number of years Claussen was involved with the local press. He first began to make a name for himself through two partially symbolic, partially realistic idylls about life in market towns, "Unge Bander" (1894) and "Kitty" (1895), which through a blend of prose and poetry as well as playfulness and grace captivated readers (particularly his introduction to "Unge Bander": "Frøken Regnvejr", likely his most significant work). Claussen later continued his depictions of Danish island life in "Pilefløjter" (1899) and "Mellem to Kyster" (1900). His small travel novels "Valfart" and "Antonius i Paris" (both 1896) are unique among his works with their poetically chatty tone. Additionally, he wrote the play "Arbejdersken".