With fiddle, uncapped device (6)
I believe the answer is:
widget
'device' is the definition.
(widget is a kind of device)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for widget that I've seen before include "Small mechanical device" , "Device used in canned beer" , "object" , "gizmo" , "Gismo" .)