Brisk, small trading place (5)
I believe the answer is:
smart
'brisk' is the definition.
(I've seen this in another clue)
'small trading place' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'trading place' becomes 'mart' (I've seen this in another clue).
's'+'mart'='SMART'
(Other definitions for smart that I've seen before include "turned out nicely" , "Quick; tidy; sting" , "Elegant and stylish" , "astute" , "Clever or stylish" .)