Dancing is inane and foolish (7)
I believe the answer is:
asinine
'foolish' is the definition.
(similar in meaning)
'dancing is inane' is the wordplay.
'dancing' is an anagram indicator.
'is'+'inane'='isinane'
'isinane' anagrammed gives 'ASININE'.
'and' acts as a link.
(Other definitions for asinine that I've seen before include "Jenny's often like this" , "simple" , "'Mindless, vacuous (7)'" , "Silly like a donkey" , "Stupid (as a donkey?)" .)