Clemens August was born in Vorhelm (now a part of Ahlen, North Rhine-Westphalia) into the Westphalian noble family of Droste zu Vischering.

[2] After completing his studies he began, in June 1796, an extensive Grand Tour, under the direction of Katerkamp, through Germany, Switzerland, and Italy, returning to Münster in August 1797.

[3] Under Prussian rule, the administrator repeatedly came into conflict with the government on account of his attitude towards the education of children of mixed marriages and the supervision of theological studies.

[3] After the death of Count von Spiegel, the incumbent of the metropolitan see of Cologne, the Prussian government, to the surprise of Catholics and Protestants alike, desired Droste zu Vischering as his successor.

When many professors at the University of Bonn refused to submit to the papal bull, Droste zu Vischering refused the imprimatur to their theological magazine, forbade the students of theology to attend their lectures, and drew up a list of anti-Hermesian theses to which all candidates for sacerdotal ordination and all pastors who wished to be transferred to new parishes were obliged to swear adherence.

The government was angered because the archbishop had enforced the papal bull without the royal approbation, but gave him to understand that it would allow him free scope in this affair, provided he would accede to its demands concerning mixed marriages.

In response, Bishops of Münster and Paderborn, fired by the example of Clemens August, revoked the assent they had formerly given to the agreement; while Martin von Dunin, the Archbishop of Gnesen (Gniezno) and Posen (Poznań), was imprisoned at Kolberg (Kołobrzeg) for the same offence that had sent Droste zu Vischering to Minden.

In an allocution of 10 December 1837, Pope Gregory XVI praised the course of the Archbishop of Cologne and solemnly protested against the action of the government.

He was permitted to retain the title of Archbishop of Cologne, but, in order to uphold the authority of the state in the public eye, was prevailed upon to select a coadjutor in the person of Johann von Geissel, Bishop of Speyer, who henceforth directed the affairs of the archdiocese.