Blasphemous behaviour (9)
I believe the answer is:
sacrilege
'blasphemous behaviour' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sacrilege that I've seen before include "Violation of something holy" , "Violation of a holy thing" , "Blasphemous behaviour" , "Blasphemy" , "Extreme disrespect for something holy" .)