European city bans naked nincompoop (7)
I believe the answer is:
antwerp
'european city' is the definition.
(I've seen this before)
'bans naked nincompoop' is the wordplay.
'naked' indicates the central letters (outside letters removed so centre is unclothed).
'nincompoop' becomes 'twerp' (I've seen this before).
The central letters of 'bans' are 'an'.
'an'+'twerp'='ANTWERP'
(Other definitions for antwerp that I've seen before include "9/11 [OLYMPIC VENUE]" , "harbour" , "Belgian city port" , "foreign city" , "Belgian port and province" .)