Popular myth surrounds quiet Scottish island (11)
I believe the answer is:
fashionable
'popular' is the definition.
('fashionable' can be similar in meaning to 'popular')
'myth surrounds quiet scottish island' is the wordplay.
'myth' becomes 'fable' (I've seen this before).
'surrounds' is an insertion indicator.
'quiet' becomes 'sh'.
'scottish island' becomes 'iona' (I've seen this before).
'sh'+'iona'='shiona'
'fable' going around 'shiona' is 'FASHIONABLE'.
(Other definitions for fashionable that I've seen before include "What's in" , "A la mode" , "Trendy" , "Modish" .)