MGibster
Legend
Druids often wear leather armor which, like plate, is created by harvesting a natural resource and using it to manufacture something that's very artificial.Druid: "I am Nature!"
Nature Cleric: "I am wearing plate."
I think the biggest difference is that a cleric acts as an intermediary between the divine and its followers. This isn't always played out in D&D games, but clerics should be involved in things like enforcing orthodoxy, interpreting and/or making religious edicts, and performing rites for the benefit of worshipers from time to time. For examples, a cleric of nature might tell the people how to thank their god properly, might interpret religious text, and lead a ceremony at the start of hunting season to ask their god for a good harvest. A druid, even one who worships the same nature god as our cleric, isn't really concerned with ministering to worshipers. Instead, the druid works with nature in the manner their god requires.
There's probably some overlap though. A druid who is responsible for maintaining a sacred grove can likely count on assistance from a cleric dedicated to the same god.