That is my interpretation of the rules and I think it was meant to be that way, so that a Cleric must choose between melee combat or combat casting. (unless he takes the War Caster Feat, of course)So, in 5th ed ... a Cleric with a Mace and a Shield can't cast spells with Somatic componets w/o droping his Mace or shield??
If that's the intention of the wording, it's probably to avoid the all-too-famous "I buff myself and run into melee, overshadowing the Fighter" Cleric gimmick.