John is able to dance (6)
I believe the answer is:
cancan
'dance' is the definition.
(I know that cancan is a type of choreography)
'john is able' is the wordplay.
'john' becomes 'can' (both can informally mean toilet).
'is able' becomes 'can' (if you can do something, you are able to do it).
'can'+'can'='CANCAN'
'to' acts as a link.
(Other definitions for cancan that I've seen before include "Parisian stage dance" , "from 23a [LA VIE PARISIENNE]?" , "High-kicking French dance, once considered naughty" , "Dance of the French music halls" , "High-kicking dance of repetitive kind" .)