Dizzy rascal has quantity for mathematicians (6)
I believe the answer is:
scalar
'quantity for mathematicians' is the definition.
I can't judge whether this definition defines the answer.
'dizzy rascal' is the wordplay.
'dizzy' indicates an anagram.
'rascal' anagrammed gives 'SCALAR'.
'has' acts as a link.
Can you help me to learn more?
(Other definitions for scalar that I've seen before include "(Quantity) with magnitude, not direction" , "graduated" , "With magnitude, not direction (maths)" , "lacking direction" .)