Thingamabob (5)
I believe the answer is:
gizmo
'thingamabob' is the definition.
(I know that thingamabob can be written as gizmo)
This is the entire clue.
(Other definitions for gizmo that I've seen before include "Gadget, thingamajig" , "Thingamabob, gadget" , "Ingenious device; gadget" , "Device or control that is very useful for a particular job" .)