Wild stay over in Brandenburg capital (7)
I believe the answer is:
potsdam
'brandenburg capital' is the definition.
(I've seen this before)
'wild stay over' is the wordplay.
'wild' becomes 'mad' ('mad' can be similar in meaning to 'wild').
'stay' becomes 'stop' (stop is a kind of stay**).
'over' is a reversal indicator.
'mad'+'stop'='madstop'
'madstop' back-to-front is 'POTSDAM'.
'in' acts as a link.
(Other definitions for potsdam that I've seen before include "WW two 1945 conference; stop mad (anag.)" , "German city" , "Brandenburg capital" , "1945 conference location" , "Site of WW2 conference" .)