Tool – cheat (6)
I believe the answer is:
chisel
I believe this is a double definition.
'tool' is the first definition.
(chisel is a kind of tool)
'cheat' is the second definition.
(I know that cheat can be written as chisel)
(Other definitions for chisel that I've seen before include "Hammered cutting tool" , "Tool used to shape wood, stone or metal" , "Carpenter's or mason's tool" , "Eg, woodworking tool" , "Slangily cheat with wood-working tool" .)