Casual dress for Milan (8)
I believe the answer is:
informal
'casual' is the definition.
('informal' can be similar in meaning to 'casual')
'dress for milan' is the wordplay.
'dress' indicates an anagram.
'for'+'milan'='formilan'
'formilan' is an anagram of 'INFORMAL'.
(Other definitions for informal that I've seen before include "Casual, not official" , "Cosy -- loose" , "If normal, be casual and without ceremony" , "Unofficial, relaxed" , "Casual, free and easy" .)