Compound in hydrogen-depleted animal skin (5)
I believe the answer is:
oxide
'compound' is the definition.
(oxide is a kind of compound)
I don't understand the remainder of the clue.
(Other definitions for oxide that I've seen before include "Compound of oxygen with another element" , "Chemical compound" , "Compound such as rust" , "Eg, rust" , "Compound of two elements, one with atomic number 8" .)