Drill that may bore (4)
I believe the answer is:
rote
'drill that may bore' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rote that I've seen before include "performance based solely on routine" , "By . . . . - from memory without thought" , "Memorisation by repetition" , "Way of learning" , "By . . . . - by memory without thinking" .)