Paul, a servant of Christ Jesus, called to be an apostle, set apart for the gospel of God,
Acts 13:2 While they were ministering to the Lord and fasting, the Holy Spirit said, "Set apart for Me Barnabas and Saul for the work to which I have called them."
to set apart means to be holy.
Are you referring to Romans 1:1?
It means that God has placed a calling on Paul. Given him a job to do.
god has a specific purpose for certain people and has set them apart for a special purpose
god sets people as paul, apart from others, to preach the gospel of god which is salvation in jesus
Set apart to the work of preaching the gospel
And with out reading it i would guess that it also means set apart from depending on anything or anyone else for salvation.
And set apart as a peculiar people different from the world because of the gospel.