The term 'Citadel of North African City' can be summarized as the Kasbah, a 6-letter word. The Kasbah is a type of fortress or citadel found in North African cities, particularly in Morocco and Algeria. It is typically a walled city with narrow streets and alleys, and is often the oldest part of a city. The Kasbah is usually the center of political and economic activity, and is often home to important monuments and landmarks.