Answer: palladium

AnswerCrossword Clue
PALLADIUMRare element harder than platinum.
PALLADIUMAtomic No. 46
palladiumanything believed to provide protection or safety; safeguard.
palladiumThe chemical element of atomic number 46, a rare silvery-white metal resembling platinum
palladiuma metallic element resembling platinum / a safeguard