I want the thalmor robes and boots for my character who is a One handed/Destruction. My question is there to have defense capability without actual armor?

Regular cloth, like robes, offer no armor if that's what you are asking.

There are spells though that raise your armor rating, and Conjuration spells that summon armor on you.

You can also enchant the clothes, but don't think there is any enchants that add armor rating to them. At any rate, even if you do get any armor rating on it through enchants I think it would be such low values that you wouldn't even notice the difference.

Basically... use spells to defend yourself if wearing just cloth... or try not to get hit

With my bow and light armor character I use a shield for upfront defense and tight places, but mostly I try to get out of the way using cover such as pillars, trees, rocks, Lydia and so on

Conjuration cannot do that anymore, but yes there are spells that act like armor.

Mage armor perk for Alteration gives you 2x protection from spells that raise Armor Class, if you're not wearing armor.

I've not seen an armor enchantment yet, but a fortify health enchantment is something like armor as well yea

There are the Oakenflesh/Stoneflesh/etc family of spells that provide you with some armor for 60 seconds. If you wear no armor at all, there's a perk for those spells that doubles their effectiveness.

Alteration have spells that increase armor rating and with perks their effect is 2x(you can invest 3 times to this perk, first one is 32x dont know after it) without any armor.
I seem to have awesome memory today.