Officer gone mad in German city (7)
I believe the answer is:
cologne
'german city' is the definition.
(I've seen this before)
'officer gone mad in' is the wordplay.
'officer' becomes 'col' (I've seen this before**).
'mad' is an anagram indicator.
'in' indicates putting letters inside.
'gone' anagrammed gives 'ogne'.
'col' inserted inside 'ogne' is 'COLOGNE'.
(Other definitions for cologne that I've seen before include "European city" , "Refreshing scent" , "smells nice" , "Eau de _____" , "Foreign city" .)