Eccentric old theologian leading dance (7)
I believe the answer is:
oddball
'eccentric' is the definition.
(an oddball is an eccentric person)
'old theologian leading dance' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'theologian' becomes 'DD' (Doctor of Divinity degree).
'leading' means one lot of letters go next to another (some letters go in front of others).
'dance' becomes 'ball' (ball is a kind of dance).
'o'+'dd'+'ball'='ODDBALL'
(Other definitions for oddball that I've seen before include "Eccentric person like uneven sphere" , "Strange, bizarre" , "Weirdo" , "Eccentric person like peculiar sphere" , "Eccentric 32" .)