A daughter of an Aboriginal shearer and an English woman, Monica was fostered at the age of seven. Monica and her brother lived in various homes in Sydney before moving to live with the Woodbury family on a farm near Spencer. Although well-loved by the Woodbury's, in 1935 Government officials removed Monica and her brother Dan from their care. The children were separated and Monica was sent to train as a domestic while Dan was sent to work on a boys' farm. After leaving the home Monica worked as a domestic for numerous families before beginning work at Wills cigarette factory. Following this she became a waitress and studied at night school to become a secretary. She became a regular visitor to the Bellwood reserve while visiting the Woodbury's who had moved to Nambucca Heads.
In 1953 she married and had a daughter, the marriage later ending in divorce. Monica was married again in 1962 to Leslie Forsyth Clare, a union official who was a advocate for Aboriginal rights. She became actively involved in the women's committee of the union and together they supported each other and highlighed the atrocious living conditions and racial discrimination inflicted upon Aboriginal people. Monica's interest in the Labor Party grew and she later became secretary of the Aboriginal committee of the South Coast Labour Council. This position enabled her reach out to politicians and pass on complaints of discrimination. She also helped establish housing and low interest loans for Aborigines.
In 1968 as secretary to the newly named South Coast Illawarra Tribe Monica led a contingent of people to assist in rehousing the Wallaga Lake and Nowra communities. As well as being a delegate to many conferences of the Federal Council for the Advancement of Aborigines and Torres Strait Islanders, she was also active on the International Women's Day, May Day and National Aborigines' Day committees.
The Monica Clare Research Fellowship is named in her honour.