Rogue crazy up in Dutch port (9)
I believe the answer is:
rotterdam
'dutch port' is the definition.
(I've seen this before)
'rogue crazy up' is the wordplay.
'rogue' becomes 'rotter' (I've seen this before).
'crazy' becomes 'mad' (synonyms).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'mad' in reverse letter order is 'dam'.
'rotter'+'dam'='ROTTERDAM'
'in' is the link.
(Other definitions for rotterdam that I've seen before include "European port" , "Dutch city and port" , "city abroad" , "Major North Sea port - tarred tom (anag)" , "foreign city" .)