Logical anaesthetic used in proportionate quantity (8,6)

I believe the answer is:

rational number

I'm a little stuck... Click here to teach me more about this clue!

'proportionate quantity' is the definition.
'rational number' can be an answer for 'quantity' (rational number is a kind of quantity). I'm unsure of the 'proportionate' bit.

'logical anaesthetic' is the wordplay.
'logical' becomes 'rational' (associated in meaning).
'anaesthetic' becomes 'number' (i.e. something that makes things numb).
'rational'+'number'='RATIONAL NUMBER'

'used in' is the link.

Can you help me to learn more?

(Another definition for rational number that I've seen is " fractional proportion".)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.