Bind up parts (5)
I believe the answer is:
strap
'bind' is the definition.
(I know that strap is a type of bind)
'up parts' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'parts' backwards is 'STRAP'.
(Other definitions for strap that I've seen before include "loopy band" , "something to hang on to" , "Fastening strip" , "Narrow strip of leather" , "Secure" .)