Refuge offered by nut? (8)
I believe the answer is:
'refuge' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for bolt hole that I've seen before include "Place into which one can escape, like a rabbit" , "Refuge when in flight" , "Private place to hide away in" , "Hiding place" , "Place of escape from danger" .)