Gangster holding plug the wrong way for gadget (6)
I believe the answer is:
doodah
'gadget' is the definition.
'gangster holding plug the wrong way' is the wordplay.
'gangster' becomes 'hood' (I've seen this before).
'holding' indicates putting letters inside.
'plug' becomes 'ad' (as in plugging a product).
'the wrong way' says the letters should be written backwards.
'hood' enclosing 'ad' is 'hadood'.
'hadood' backwards is 'DOODAH'.
'for' acts as a link.
(Other definitions for doodah that I've seen before include "Whatsit" , "Gizmo, thingamabob" , "Thingamy" , "thingumajig" , "Whatsitsname" .)