Complex sentence: Suffragettes were members of women's organisation (right to vote) movements in the late 19th and early 20th century, particularly militants in Great Britain such as members of the Women's Social and Political Union (WSPU).
Split into simpler sentences: Suffragettes were members of women's organisations in the late 19th and early 20th century which advocated the extension of the Franchise to women. It particularly refers to militants in Great Britain such as members of the Women's Social and Political Union (WSPU).