Paradoxically they could be evens (4)
I believe the answer is:
odds
'they could be evens' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for odds that I've seen before include "Estimate of likelihood" , "Variance" , "Chances of occurrence" , "Betting ratio" , "ten to one?" .)