Eccentric's love doubled outside dance (7)
I believe the answer is:
oddball
'eccentric's' is the definition.
('oddball' can be a synonym of 'eccentric')
'love doubled outside dance' is the wordplay.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'outside' suggests removing the centre.
'dance' becomes 'ball' (ball is a kind of dance).
'doubled' with its middle removed is 'dd'.
'o'+'dd'+'ball'='ODDBALL'
(Other definitions for oddball that I've seen before include "eccentric type" , "Eccentric person like peculiar sphere" , "Crackpot" , "Crank" , "Eccentric person (colloq.)" .)