Fastening different parts (5)
I believe the answer is:
strap
'fastening' is the definition.
'different parts' is the wordplay.
'different' is an anagram indicator (letters placed in a different order).
'parts' with letters rearranged gives 'STRAP'.
(Other definitions for strap that I've seen before include "Secure" , "Restraining fastener" , "Narrow strip of leather" , "e.g. Belt" , "Belt; leather strip" .)