Ostensibly only Milan adapted (9)
I believe the answer is:
nominally
'ostensibly' is the definition.
(thesaurus)
'only milan adapted' is the wordplay.
'adapted' indicates an anagram.
'only'+'milan'='onlymilan'
'onlymilan' is an anagram of 'NOMINALLY'.
(Other definitions for nominally that I've seen before include "In name only" , "In theory" , "Theoretically" .)