Cruise missile test backed by a person favouring war (8)
I believe the answer is:
tomahawk
'cruise missile' is the definition.
(I know that Tomahawk is a type of cruise missile)
'backed by a person favouring war' is the wordplay.
'backed by' says to put letters next to each other.
'a person' becomes 'hawk' (hawk is a kind of person).
'favouring war' becomes 'toma' (I can't justify this - if you can you should believe this answer much more).
'hawk' put after 'toma' is 'TOMAHAWK'.
'test' is the link.
This may not be correct. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for tomahawk that I've seen before include "Native American war-axe" , "Traditional North American fighting axe" , "Brave's hatchet" , "killer on reservation?" , "Native American weapon" .)