Metal ore (7)
I believe the answer is:
mineral
'metal ore' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mineral that I've seen before include "Neither animal nor vegetable" , "E.g. bauxite, quartz" , "Made from inorganic matter" , "Zinc or magnesium, say" , "Mined substance" .)