In the Dark Age of Camelot sense, a Cleric is an Acolyte that joins the Church of Albion upon seasoning their fifth. Clerics may wield one-handed crushing weapons and wear leather armour. On the tenth season, clerics are granted the ability to wear studded armour. On their 20th, chain mail. When an acolyte joins The Church, the Smiting specialization line is added to their Enhancement and Rejuvenation skill lines.
As the cleric progresses, they learn direct damage spells and stunning spells in the Smiting line. Without this line, a cleric's only offense is his hammer and his only defense is his armour and discretion in his valor. Specialization in this line yields direct damge spells of greater potency, an area effect spell version of the direct damage spell, a point blank area effect (PBAE) mesmerization spell and a stacking self damage blessing (buff.) However, since there is a Wizard class in DAoC, and wizards do not have the advantage of the cleric's chain mail armour, the cleric's smiting ability was lessened so that it is almost wholly eclipsed by the cleric's other abilities.
The Enhancement line is the second most valuble skill line of the cleric. From this line, clerics learn increasingly powerful armour factor (efficacy) buffs, strength buffs, constitution buffs, and, my personal favorite, dexterity buffs. Specializing in enhancement yields combination buffs: strength and constitution, dexterity and quickness. Because clerics are limited in the number of buffs they can sustain, these combination buffs are almost always better than any single statistic buff. Specializing in enhancement also grants another armour factor buff (which stacks with the first,) an intelligence buff, a health regeneration rate buff which is essentially worthless, and a self melee buff which stacks with that of the smiting line. Finally, clerics are granted a variety of spell resistance buffs which cost no concentration on the part of the cleric and are effective throughout the cleric's group.