Not one over the eight! (5)
I believe the answer is:
seven
This might be a double definition.
'not one over' is the first definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?
'the eight' is the second definition.
The answer and definition can be both quantities as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
Can you help me to learn more?
(Other definitions for seven that I've seen before include "Number of sins, seas or dwarves" , "Number (of stars in the sky?)" , "See 1" , "Number of seas sailed?" , "Number of colours of the rainbow" .)