Friendly German keeps working for aggressive type (9)
I believe the answer is:
warmonger
'aggressive type' is the definition.
'friendly german keeps working' is the wordplay.
'friendly' becomes 'warm' (associated in meaning).
'german' becomes 'ger' (abbreviation).
'keeps' means one lot of letters goes inside another (inserted letters are kept inside).
'working' becomes 'on' (e.g. a machine is working or on).
'warm'+'ger'='warmger'
'warmger' enclosing 'on' is 'WARMONGER'.
'for' is the link.
(Other definitions for warmonger that I've seen before include "Aggressor" , "Bellicose person" , "Hawk" , "Belligerent person" , "Jingoist" .)