___ odds (50-50 chance) (4)
'odds' is the definition.
(I've seen this in other clues)
This is the entire clue.
(Other definitions for evens that I've seen before include "Likelihood" , "Level betting" , "Fifty-fifty odds" , "Half a chance" , "Bookies' odds matching the amount staked" .)
(Other definitions for are that I've seen before include "Unit of land measure equal to 100 square metres" , "(We/they/you) exist" , "is for more than one" , "Is, in the plural" , "live" .)
(Other definitions for even that I've seen before include "Yet; level" , "Flush" , "Still - divisible by two" , "Level, calm" , "Describes a number divisible by two" .)