Complex sentence: The Communist Party of Great Britain (Marxist--Leninist) is a Marxist-Leninist and anti-imperialist political party in the United Kingdom, active in England, Scotland, and Wales.
Split into simpler sentences: The Communist Party of Great Britain (Marxist--Leninist) is a Marxist-Leninist and anti-imperialist political party in the United Kingdom. The CPGB-ML is a British Communist party active in England, Scotland, and Wales.