Twice, Everyman's beginning to take against nephew: that's not odd (4)
I believe the answer is:
even
'not odd' is the definition.
('even' is the opposite to 'odd')
'twice everyman's beginning to take against nephew' is the wordplay.
I cannot quite see how this works, but
'against' could be 'v' (abbreviation for 'versus') and 'v' is located in the answer.
The remaining letters 'een' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'that's' is the link.
Can you help me to learn more?
(Other definitions for even that I've seen before include "Plumb" , "Like half the numbers" , "Constant" , "Not easily annoyed" , "When darkness starts to fall" .)