Tintin's naughty knees-up? (6)
I believe the answer is:
cancan
'naughty knees-up?' is the definition.
(suggestive dance)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for cancan that I've seen before include "Lively stage dance, doubly permissive" , "Daring French dance, doubly permissive" , "Parisian stage dance" , "High-kicking dance of a female chorus line" , "Lively French stage dance" .)