Rash treatment
I believe the answer is:
talc
'rash treatment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for talc that I've seen before include "Mica - scented body powder" , "Bathroom powder (abbr)" , "In brief, popular body powder" , "Toilet powder - mica" , "Softest mineral on Mohs hardness scale" .)