The term 'Uganda Tyrant' refers to Idi AMIN, the former president of Uganda who ruled from 1971 to 1979. AMIN was a military dictator who was known for his oppressive and violent rule, as well as his expulsion of the Asian population from Uganda. He was also responsible for the deaths of hundreds of thousands of people during his reign. The four-letter solution to the crossword is AMIN, which is the last name of Idi AMIN.