'Cosmopolitan' dictates I shop after a fashion (13)
I believe the answer is:
sophisticated
'cosmopolitan' is the definition.
('sophisticated' can be similar in meaning to 'cosmopolitan')
'dictates i shop after a fashion' is the wordplay.
'after a fashion' indicates an anagram.
'dictates'+'i'+'shop'='dictatesishop'
'dictatesishop' with letters rearranged gives 'SOPHISTICATED'.
(Other definitions for sophisticated that I've seen before include "Possessed of culture, refinement and 24" , "Worldly" , "Showing knowledge of fashion and culture" , "Cultured; elegant" , "Urbane" .)