Sign for dance heads removed, showing lack of insight (9)
I believe the answer is:
ignorance
'lack of insight' is the definition.
(ignorance is a lack of knowledge or insight)
I don't understand the rest of the clue.
(Other definitions for ignorance that I've seen before include "Lack of education" , "Unintelligence" , "State of unknowing" , "......... of the law is no excuse for breaking it" , "Lack of knowledge" .)