Plane is not dismantled for scrap (8)
I believe the answer is:
jettison
'for scrap' is the definition.
(I've seen this before)
'plane is not dismantled' is the wordplay.
'plane' becomes 'jet' (jet is a kind of plane).
'dismantled' indicates an anagram.
'is'+'not'='isnot'
'isnot' with letters rearranged gives 'tison'.
'jet'+'tison'='JETTISON'
(Other definitions for jettison that I've seen before include "Eject" , "Throw (into the sea)" , "Form of motor racing" , "Chuck overboard" , "Throw goods overboard, or discard what is unwanted" .)