Complex sentence: Cliff, meanwhile, has been hired by his pompous brother-in-law, Lester (Alda), a successful television producer to make a documentary celebrating Lester, whom he grows to actively despise.
Split into simpler sentences: Cliff, meanwhile, is hired by his pompous brother-in-law, Lester (Alda), a successful television producer. Cliff is to make a documentary celebrating Lester, whom he grows to actively despise.