Bush says piece as politician (5,9)
I believe the answer is:
elder statesman
'politician' is the definition.
(elder statesman is a kind of politician)
'bush says piece' is the wordplay.
'bush' becomes 'elder' (elder is a kind of bush).
'says' becomes 'states' (state can mean to say or declare).
'piece' becomes 'man' (man can mean a chess piece).
'elder'+'states'+'man'='ELDER STATESMAN'
'as' acts as a link.
(Other definitions for elder statesman that I've seen before include "veteran politician - with 17d" , "Wise old politician" , "John Major?" , "Experienced politician" , "Perhaps Clinton" .)