Reveller said bet on outsider (12)
I believe the answer is:
bacchanalian
'reveller' is the definition.
(I have seen 'drunken reveller' mean 'bacchanalian' so perhaps 'reveller' could also mean 'bacchanalian')
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for bacchanalian that I've seen before include "Relating to drunken revelry" , "Drunken, orgiastic (revel)" , "drunken reveller" , "description of drunken revels" .)