When a recipe calls for 1 shallot , does it mean the whole bulb, or one of the cloves?

1 "clove" or piece equals a shallot. It's really no different than any other recipe that has non exact measurements ( medium onion, large apple, etc)
Cook with the amount that feels and tastes right to you.

I could be way wrong, but I think of one shallot as one of the cloves, about a quarter cup minced. But as long as you're cooking it, you probably can't have too much shallot.

I hate it when a recipe specifies 1 shallot or 1 small onion, especially if it is a recipe where too much would overwhelm and ruin a recipe. It makes so much sense to specify 1 tablespoon or 1/2 cup or a universally measurable amount.

Shallots vary a lot in size. If you feel comfortable, you should just use your personal preference.. Otherwise, use the whole bulb.