A profession, or as we usually say, a vocation (1 Corinthians 7:20). The "hope of your calling" in Ephesians 4:4 is the hope resulting from your being called into the kingdom of God.

CALLING, n.

1. A naming, or inviting; a reading over or reciting in order, or a call of names with a view to obtain an answer, as in legislative bodies.

2. Vocation; profession; trade; usual occupation, or employment.

Pope. Swift. 1 Cor. 7:20

3. Class of persons engaged in any profession or employment.

4. Divine summons, vocation, or invitation.

Give all diligence to make your calling and election sure. 2 Pet. 1.