Simple chap isn't used to travelling round Italy (15)
I believe the answer is:
unsophisticated
'simple' is the definition.
(similar in meaning)
'chap isn't used to travelling round italy' is the wordplay.
'travelling' indicates an anagram.
'round' is an insertion indicator.
'italy' becomes 'i'.
'chap'+'isnt'+'used'+'to'='chapisntusedto'
'chapisntusedto' with letters rearranged gives 'unsophistcated'.
'unsophistcated' enclosing 'i' is 'UNSOPHISTICATED'.
(Other definitions for unsophisticated that I've seen before include "Simple" , "crude" , "straightforward" , "Lacking experience" , "green" .)