Smart number after change of leader (5)
I believe the answer is:
nifty
'smart' is the definition.
(nifty can mean stylish)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for nifty that I've seen before include "Particularly effective; stylish" , "Smart" , "Slick" , "Clever; stylish" , "Quick - stylish" .)