Wise leader says piece (9)
I believe the answer is:
statesman
'wise leader' is the definition.
'statesman' can be an answer for 'leader' (statesman is a kind of leader). I am not sure about the 'wise' bit.
'says piece' is the wordplay.
'says' becomes 'states' (state can mean to say or declare).
'piece' becomes 'man' (man can mean a chess piece).
'states'+'man'='STATESMAN'
Can you help me to learn more?
(Other definitions for statesman that I've seen before include "Experienced politician" , "Respected politician" , "Eminent politician" , "Government minister" , "Political leader" .)