Be able to repeat a vigorous dance (6)
I believe the answer is:
cancan
'a vigorous dance' is the definition.
'cancan' can be an answer for 'dance' (cancan is a kind of dance). I'm unsure of the 'a vigorous' bit.
'be able to repeat' is the wordplay.
'be able' becomes 'can'.
'to repeat' says to double the letters.
'can' duplicated is 'CANCAN'.
Can you help me to learn more?
(Other definitions for cancan that I've seen before include "Lively stage dance, doubly permissive" , "French female chorus line dance" , "Leg-kicking dance" , "Chorus-line dance" , "Parisian high-kicking dance" .)