Fasteners changing scale (5)
I believe the answer is:
laces
'fasteners' is the definition.
'changing scale' is the wordplay.
'changing' indicates an anagram.
'scale' with letters rearranged gives 'LACES'.
(Other definitions for laces that I've seen before include "Scale for shoe securers" , "Shoe ties" , "Cords for fastening shoes" , "Shoestrings" , "Cords for tying shoes" .)