Establish core unit prepared to defend Germany (9)
I believe the answer is:
introduce
'establish' is the definition.
(thesaurus)
'core unit prepared to defend germany' is the wordplay.
'prepared' is an anagram indicator.
'to defend' is an insertion indicator.
'germany' becomes 'd' (international vehicle registration code).
'core'+'unit'='coreunit'
'coreunit' with letters rearranged gives 'introuce'.
'introuce' enclosing 'd' is 'INTRODUCE'.
(Other definitions for introduce that I've seen before include "Provide an opening announcement for" , "Bring in for the first time" , "Propose" , "Start; present" , "Bring into use by way of reduc tion" .)