Complex sentence: He became the "secretary" of the interprovincial Sicilian Mafia Commission that was formed around 1975 on the instigation of Calderone to coordinate the provincial Mafia commissions and avoid conflicts over public contracts that crossed provincial borders.
Split into simpler sentences: He became the "secretary" of the interprovincial Sicilian Mafia Commission, formed around 1975 on his instigation. It coordinated the provincial Mafia commissions and avoided conflicts over public contracts that crossed provincial borders.