Drill jade (4)
I believe the answer is:
I believe this clue is a double definition.
'drill' is the first definition.
(I know that drill can be written as bore)
'jade' is the second definition.
(Other definitions for bore that I've seen before include "Wearisome person" , "Make a hole with a pointed tool" , "Pierce or tire with tedium" , "Hollow barrel" , "Dull person; hole" .)