Drills black minerals (5)
I believe the answer is:
bores
'drills' is the definition.
('bore' can be a synonym of 'drill')
'black minerals' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'minerals' becomes 'ores' (ore is a kind of mineral).
'b'+'ores'='BORES'
(Other definitions for bores that I've seen before include "Drills or wearies" , "Dull tedious talkers" , "Tedious people or drills" , "Makes a hole with a pointed tool" .)