Complex sentence: Clive Donner (21 January 1926, London--7 September, 2010) was a British film director who started his career in the mid- 1950s after working as a film editor (most notably on the comedy "Genevieve", made in 1953).
Split into simpler sentences: Clive Donner (21 January 1926--7 September, 2010) was a British film director. Donner was born in London and started his career in the mid- 1950s after working as a film editor (most notably on the comedy "Genevieve", made in 1953).