Well-kept small trading centre (5)
I believe the answer is:
smart
'well-kept' is the definition.
(I've seen this before)
'small trading centre' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'trading centre' becomes 'mart' (I've seen this before).
's'+'mart'='SMART'
(Other definitions for smart that I've seen before include "astute" , "Posh" , "Elegant and stylish" , "Bright or dapper" , "Clever - feel mild pain" .)