Married love captivates Irish eccentric (6)
I believe the answer is:
weirdo
'eccentric' is the definition.
(I've seen this before)
'married love captivates irish' is the wordplay.
'married' becomes 'wed' (wed can mean married).
'love' becomes 'o' (love means zero in tennis).
'captivates' indicates putting letters inside (inserted letters are captured or captivated).
'irish' becomes 'IR' (abbreviation for Irish).
'wed'+'o'='wedo'
'wedo' going around 'ir' is 'WEIRDO'.
(Other definitions for weirdo that I've seen before include "Nutcase" , "Informally, an eccentric or very strange person" , "Derogatory term for an eccentric" , "Odd bod" , "Odd type" .)