[Anthony]

Clerics, relative to DF dedicated combatants, simply aren't very good with weapons, so attacking with whatever weapon you use is likely to be a minor concern; mostly, what you are looking at is 'how good is this thing at preventing me from being killed'.

Looking at your options as a cleric:
Staff-15: You get one parry (at 12), and a second parry (at 8), which is likely no better than your dodge (likely Light encumbrance, so 8). Against ranged attacks, defense is always 8. Your weapon can be a Staff. If you do attack, 1d+5 (2d+1) crush, and it is the only weapon here with reach.
Shield+Flail: assuming a medium shield, you get one block (at 12), one parry (at 11), and then subsequent attacks would be Dodged (likely medium encumbrance, so 9). Against ranged attacks, one parry at 12, one dodge at 9. If your flail is not Dwarven, parrying will prevent attacking. If you do attack, 1d+5 crush.
Shield+Axe/Mace: assuming a medium shield, you get one block (at 12), one parry (at 12), and then subsequent attacks would be Dodged (likely medium encumbrance, so 9). Against ranged attacks, one parry at 12, one dodge at 9. If your axe/mace is not Dwarven, parrying will prevent attacking. If you do attack, 1d+5 crush or 1d+4 cut.
Shield+Broadsword: assuming a medium shield, you get one block (at 12), one parry (at 12), and then subsequent attacks would be Dodged (likely medium encumbrance, so 9). Against ranged attacks, one parry at 12, one dodge at 9. If you attack, a broadsword does 1d+3 cut, but you can also use a short staff one-handed with broadsword skill; damage is lousy (1d+2 crush) but it can be enchanted with Staff.

Shield plus staff (using broadsword skill) would probably be my choice, but all of these options have virtues.