Missile trailing plane's wreckage (6)
I believe the answer is:
jetsam
'wreckage' is the definition.
(jetsam is a kind of wreckage)
'missile trailing plane's' is the wordplay.
'missile' becomes 'sam' (abbreviation for surface-to-air missile).
'trailing' says to put letters next to each other.
'plane' becomes 'jet' (jet plane is a kind of plane).
'sam' after 'jet' is 'JETSAM'.
(Other definitions for jetsam that I've seen before include "Goods jettisoned from a ship and washed up on shore" , "Discarded rubbish" , "Unwanted material thrown overboard" , "it is scattered at sea" , "Discarded objects washed ashore" .)