Nook's counterpart (6)
I believe the answer is:
cranny
'nook's counterpart' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cranny that I've seen before include "Crevice, goes with nook" , "Small rock fissure" , "Fissure - chink" , "Secret place (searched after nook)" , "Crevice as hiding place" .)