Suggest a possible case for secret police (7)
I believe the answer is:
gestapo
'secret police' is the definition.
(Nazi secret police)
'suggest a possible case' is the wordplay.
'case' says the answer is hidden in the clue (I've seen 'cases' mean this).
'GESTAPO' is hidden in the letters of 'suggest a possible'.
'for' is the link.
(Other definitions for gestapo that I've seen before include "Nazi Germany's secret state police" , "Hitler's secret police" , "Notorious secret police" , "Police detested" , "State police in Nazi Germany" .)