My prefix is a bamboozling.
A con is a bamboozling.
My infix is tantilizing.
To tempt is to tantalize.
My suffix is full.
ous is a suffix from Latin for full.
My whole is disdainful.
Contemptuous means disdainful.
Element partially responsible for destruction of an evil city (6)
Credit to ferret for sulfur, which destroyed Sodom and Gomorrah.
With two I'm silvery white.
Ce is the symbol for Cesium, which is silvery-white (according to some sources).
With four I'm a cover for nostrils.
A cere covers bird nostrils.
With all six I'm a food.
Cereal is a food.
There is hidden text before each puzzle, which combined with the answers yields the cryptic clue "Be contemptuous of sulfur put on cereal (5)." The answer is scorn, which means "be contemptuous", and scorn = s + corn where s = sulfur and corn = cereal.