Wrench or hammer (4)
This clue is a double definition.
'wrench' is the first definition.
(thesaurus)
'hammer' is the second definition.
(I've seen this in another clue)
(Other definitions for tool that I've seen before include "organ" , "Maybe saw" , "Working instrument" , "Hand implement" , "Person used by another" .)
(Other definitions for hand tool that I've seen before include "No old hat (anag) -- chisel, for example" , "Plane, for example - no old hat (anag)" , "Such as a drill or sander" .)