Mineral discovered by wicked sort, we hear, by pub (8)
I believe the answer is:
cinnabar
'mineral' is the definition.
(I've seen this before)
'wicked sort we hear by pub' is the wordplay.
'wicked sort' becomes 'sinner'.
'we hear' indicates a 'sounds like' (homophone) clue.
'by' means one lot of letters go next to another.
'pub' becomes 'bar' (I've seen this before).
'sinner' sounds like 'cinna'.
'cinna'+'bar'='CINNABAR'
'discovered by' is the link.
(Other definitions for cinnabar that I've seen before include "Red mercury sulphide" , "Bright red mineral containing mercury" , "Heavy red mineral containing mercury" , "Brian can make vermilion pigment" .)