Unmatched son's chances (4)
I believe the answer is:
odds
'chances' is the definition.
(the odds of something happening)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for odds that I've seen before include "prices" , "Ratios set by bookies" , "Variance" , "at which one may be disagreeing" , "inequality" .)