50-50 odds (5)
I believe the answer is:
evens
'50-50 odds' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for evens that I've seen before include "less likely than 27 [ODDS-ON]" , "Odds on something very likely to win" , "Odds that win identical sum as the stake" , "Makes equal" , "Kind of betting odds on seven" .)