Mineral softer than gypsum (4)
I believe the answer is:
talc
'mineral softer than gypsum' 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" , "Fragrant powder" , "Drier" , "Soft white powder" , "Fine powder" .)