Spear is fine
Unless you're a dwarf, elf, or some other race that gives weapon proficiencies, clerics can only use (with proficiency) simple weapons anyway (excluding domains that grant martial weapon proficiency), which means that with a shield you can only wield a one-handed weapon that has at most a d6 damage die. So at that point, whether you pick a spear over a mace (the typical default cleric weapon, unless you're a dwarf, then it's a warhammer) makes no difference in terms of damage output.
The spear does piercing damage, so if you are fighting a creature with vulnerability to bludgeoning damage like a skeleton, then the mace or warhammer would be better, but that's very situational (more of interest if considering choices for backup weapons).
However, if you are a dwarf or an elf and could therefore could pick a warhammer or longsword, which uses a d8 damage die, then it is the mechanically better option over a spear, but D&D doesn't have to be all about min-maxing. You'd still be fine with a spear of that's what you want your character to use.