Stop German report (4)
I believe the answer is:
bang
'report' is the definition.
(report can mean a loud noise)
'stop german' is the wordplay.
'stop' becomes 'ban' (I've seen this in other clues).
'german' becomes 'g' (abbreviation).
'ban'+'g'='BANG'
(Other definitions for bang that I've seen before include "Loud noise; fringe" , "Strike violently" , "Sound of explosion" , "Sudden impact" , "drug injection" .)