Things not on the level or square, not first class (10)
I believe the answer is:
inequality
This might be a double definition.
'things not on the level' is the first definition.
(things not being equal or level)
'square not first class' is the second definition.
The definition and answer can be both human attributes as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'or' acts as a link.
Can you help me to learn more?
(Another definition for inequality that I've seen is " Disparity".)