Twenty Questions category (7)
I believe the answer is:
mineral
'twenty questions category' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mineral that I've seen before include "Made from inorganic matter" , "Gypsum or magnesia, say" , "Gypsum or magnesium, say" , "ore, possibly" , "Such as 1 dn" .)