Part of workshop that is failing (4)
I believe the answer is:
vice
I believe this is a double definition.
'part of workshop' is the first definition.
(tool in a workshop)
'is failing' is the second definition.
(a moral failing)
'that' is the link.
(Other definitions for vice that I've seen before include "Getting a grip" , "may have a powerful grip" , "One that grips" , "In place of - depravity" , "Gripper - in place of - immorality" .)