Pianist-politician was irked, sadly, about second of legs supporting piano (10)
I believe the answer is:
paderewski
'pianist' is the definition.
(Polish pianist Ignacy Paderewski)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for paderewski that I've seen before include "Former key player" , "Ignace Jan -, Polish pianist and statesman" , "in Polish politics" , "Pianist who became Poland's prime minister in 1919" , "Polish pianist and politician" .)