German prison camp (6)
I believe the answer is:
stalag
'german prison camp' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stalag that I've seen before include "German camp for POWs" , "German prison camp in WW2" , "German World War two prison camp" , "German POW camp in WWII" , "German prisoner-of-war camp of WW2" .)