Slenderness is a noun. A noun is a type of word the meaning of which determines reality.

What does it mean to clad something?

transitive verb. : sheathe, face specifically : to cover (a metal) with another metal by bonding stainless steel plates were clad with copper.

What does being slender mean?

As applied to the human body, slender implies a generally attractive and pleasing thinness: slender hands. Slight often adds the idea of frailness to that of thinness: a slight, almost fragile, figure. Slim implies a lithe or delicate thinness: a slim and athletic figure.