They work with a tool (6)
I believe the answer is:
pliers
I believe this clue is a double definition.
'they work' is the first definition.
(ply means to work steadily)
'a tool' is the second definition.
(pliers is a kind of tool)
'with' is the link.
(Other definitions for pliers that I've seen before include "Gripping tool with two serrated jaws" , "Pinching or gripping tool" , "Wire benders" , "Workmen's tools" , "Tool with jaws for gripping small objects" .)