Even, as odds (3-2-3)
I believe the answer is:
one-to-one
'even as odds' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for one-to-one that I've seen before include "meeting?" , "T?te-?-t?te" , "Corresponding uniquely, each to another" , "12:59" .)