Lively Bohemian dance (5)
I believe the answer is:
'lively bohemian dance' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for polka that I've seen before include "Dance originally from part of 1 across" , "Dot may be associated with this" , "Folk dance" , "a merry dance?" , "Bohemian dance with three steps and a hop" .)