Fastening, knotting (5)
I believe the answer is:
tying
I believe this is a double definition.
'fastening' is the first definition.
(I know that tying is a type of fastening)
'knotting' is the second definition.
(I've seen this in another clue)
(Other definitions for tying that I've seen before include "Scoring the same" , "Linking" , "restrictive" , "Binding, fastening" , "lacing" .)