Postage for secret police (7)
I believe the answer is:
gestapo
'secret police' is the definition.
(Nazi secret police)
'postage' is the wordplay.
'postage' can be anagrammed to 'GESTAPO'.
However, I am not clear how the anagram is indicated.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for gestapo that I've seen before include "Brutal force" , "Police detested" , "Hitler's secret police" , "State police in Nazi Germany" , "war force" .)