The part that makes the hole (3)
I believe the answer is:
bit
'the part' is the definition.
(both mean a piece of something)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for bit that I've seen before include "Mouthpiece of brindle or tip of drilling tool" , "Between horse's teeth, this loses control" , "Segment" , "Morsel" , "Took effect - fragment" .)