Occasional dance is eccentric (7)
I believe the answer is:
oddball
'is eccentric' is the definition.
(an oddball is an eccentric person)
'occasional dance' is the wordplay.
'occasional' becomes 'odd' (odd can mean occasional or infrequent).
'dance' becomes 'ball' (ball is a kind of dance).
'odd'+'ball'='ODDBALL'
(Other definitions for oddball that I've seen before include "Crackpot" , "Unusual" , "Eccentric person like uneven sphere" , "eccentric type" , "Strange person (colloq.)" .)