Since an overseer is entrusted with God's work, he must be blameless- not overbearing, not quick-tempered, not given to drunkenness, not violent, not pursuing dishonest gain. Rather, he must be hospitable, one who loves what is good, who is self-controlled, upright, holy and disciplined. He must hold firmly to the trustworthy message as it has been taught, so that he can encourage others by sound doctorine and refute those who oppose it.
(Titus 1: 7-9)
Note: An overseer is traditionally the bishop of the church and he serves the role of a leader too.

Paul wanted Titus to be a perfect leader, one that does not give in to temptation and pleasure, one that is honest and self-disciplined. He wanted Titus serve the Lord, and to preach God's message to others.