Use a drill (8)
I believe this is a double definition.
'use' is the first definition.
(I know that use can be written as exercise)
'a drill' is the second definition.
(I know that drill can be written as exercise)
(Other definitions for exercise that I've seen before include "keep physically fit" , "Practice piece of work" , "Keep-fit" , "Employment" , "School task; drill" .)
'use a drill' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bore that I've seen before include "Hollow out; dull person" , "Drill or weary" , "Weary with tediousness" , "Drill to be tiresome" , "Calibre of gun - nuisance" .)