Oddball rector interrupts wedding vow after draining wine (6)
I believe the answer is:
weirdo
'oddball' is the definition.
(I've seen this in another clue)
'rector interrupts wedding vow after draining wine' is the wordplay.
'rector' becomes 'r'.
'interrupts' is an insertion indicator.
'wedding vow' becomes 'I do' ('I do' is part of the traditional wedding vows).
'after' means one lot of letters go next to another.
'draining' says to hollow out the word (remove centre letters) (I've seen 'drained' mean this).
'wine' with its centre removed is 'we'.
'r' going within 'ido' is 'irdo'.
'irdo' put after 'we' is 'WEIRDO'.
(Other definitions for weirdo that I've seen before include "Informally, an eccentric or very strange person" , "queer fish" , "Nutcase" , "Crank - oddball" , "Informally, an odd or eccentric person" .)