Fastening hole (6)
I believe the answer is:
eyelet
'fastening hole' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for eyelet that I've seen before include "Hole in needle through which thread passes" , "Small hole through which a cord is passed" , "Small ring, for shoelace perhaps" , "Hole in shoe through which lace passes" , "Small reinforced hole" .)