Black mineral in hole (4)
I believe the answer is:
bore
'hole' is the definition.
(thesaurus)
'black mineral' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'mineral' becomes 'ore' (ore is a kind of mineral).
'b'+'ore'='BORE'
'in' acts as a link.
(Other definitions for bore that I've seen before include "Drill a hole in" , "Weary with tediousness" , "Fast-running water" , "River wave; drill" , "Pierce - weary - tidal flood" .)