Conflict with the German prison officer (6)
I believe the answer is:
warder
'prison officer' is the definition.
(I've seen this before)
'conflict with the german' is the wordplay.
'conflict' becomes 'war' (war is a kind of conflict).
'with' means one lot of letters go next to another.
'the german' becomes 'der' ('the' in German).
'war'+'der'='WARDER'
(Other definitions for warder that I've seen before include "keeper" , "Gaoler" , "Reward for prison guard" , "screw" , "Jailer" .)