Now, as some might say, a number less than one (3)

'a number less than one' is the definition.
I know nothing about this answer so I can't judge whether this works.

'now as some might say' is the wordplay.
'now as' becomes 'no' (I am not sure about this - if you are sure you should believe this answer much more).
'some' means to look at the middle letters.
'might' becomes 'power' (being mighty).
'say' indicates a 'sounds like' (homophone) clue.
The middle of 'power' is 'owe'.
'owe' is a homophone of 'o'.
'no'+'o'='NOO'

Can you help me to learn more?