Style of piano jazz (6-6)
I believe the answer is:
boogie-woogie
'style of piano jazz' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for boogie-woogie that I've seen before include "Fast piano blues style" , "Style of blues played on the piano" , "Style of blues playing" , "Style of piano jazz" .)