Trouble holding double plastic bomb (9)
I believe the answer is:
doodlebug
'bomb' is the definition.
(I know that doodlebug is a type of cruise missile)
'trouble holding double plastic' is the wordplay.
'trouble' becomes 'dog' (dog can mean to trouble or plague someone).
'holding' indicates putting letters inside.
'plastic' indicates an anagram (plastic can mean easily moulded).
'double' with letters rearranged gives 'odlebu'.
'dog' placed around 'odlebu' is 'DOODLEBUG'.
(Other definitions for doodlebug that I've seen before include "may be cruise missile" , "WWII weapon" , "WWII flying bomb - mineral detector" , "German bomb otherwise known as a V-1" , "WW2 rocket" .)