Aggressor discovered peace in West Germany (9)
I believe the answer is:
warmonger
'aggressor' is the definition.
(I've seen this before)
'peace in west germany' is the wordplay.
I cannot really see how this works, but
'west' could be 'w' (abbreviation) and 'w' is located in the answer.
'germany' could be 'ger' (I've seen this in other clues) and 'ger' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'discovered' acts as a link.
(Other definitions for warmonger that I've seen before include "Hawk" , "Bellicose person" , "Hitler, perhaps" , "Jingoist" , "Aggressor" .)