Complex sentence: In 1931, Clynes sided with Arthur Henderson and George Lansbury against MacDonald's support for austerity measures to deal with the Great Depression and split with MacDonald when he left Labour to form a National Government.
Split into simpler sentences: In 1931, Clynes sided with Arthur Henderson and George Lansbury, against MacDonald's support for austerity measures to deal with the Great Depression. Clynes split with MacDonald when the latter left Labour to form a National Government.