It's used in oriental cosmetics (4)
I believe the answer is:
talc
'it's' is the definition.
I can't judge whether this definition defines the answer.
'in oriental cosmetics' is the wordplay.
'in' indicates a hidden word.
'TALC' is hidden within 'oriental cosmetics'.
'used' is the link.
Can you help me to learn more?
(Other definitions for talc that I've seen before include "soother" , "Mica - scented body powder" , "Fragrant powder" , "Scented powder used after bathing" , "Soft white powder" .)