Fashionable southern trading centre (5)
I believe the answer is:
smart
'fashionable' is the definition.
(similar in meaning)
'southern trading centre' is the wordplay.
'southern' becomes 's' (abbreviation).
'trading centre' becomes 'mart' (I've seen this before).
's'+'mart'='SMART'
(Other definitions for smart that I've seen before include "Trim - sting" , "Clean and stylish" , "Neat, tidy; sting" , "Alick" , "Quick - trim" .)