Hawk and wren Margo trained (9)
I believe the answer is:
warmonger
'hawk' is the definition.
(thesaurus)
'wren margo trained' is the wordplay.
'trained' is an anagram indicator (to train can mean to grow something into a shape).
'wren'+'margo'='wrenmargo'
'wrenmargo' with letters rearranged gives 'WARMONGER'.
'and' acts as a link.
(Other definitions for warmonger that I've seen before include "Hawk" , "Hitler, perhaps" , "Bellicose type" , "Belligerent person" , "Aggressor" .)