[citation needed] He studied moral theology at the Gregorian University, obtaining a licentiate in 1976.

[1] He then joined the Roman Curia as first secretary and then, before the end of 1984, study assistant of the Congregation for the Doctrine of the Faith with the role of personal secretary to the prefect of the congregation, Cardinal Joseph Ratzinger, the future Pope Benedict XVI.

[3] On 25 November of the same year, he was appointed Secretary of the Pontifical Council for the Laity and Titular Bishop of Segermes.

[2] As Secretary of the Pontifical Council for the Laity, he organized several World Youth Day celebrations: Cologne (2005), Sydney (2008), Madrid (2011), Rio de Janeiro (2013) and Krakow (2016).

[2] In November 2020, Clemens was named papal delegate to Klosterneuburg Monastery in Austria, an Augustinian institution troubled by charges of sexual abuse.