Ask if there’s a willingness to buy (6)

I believe the answer is:

demand

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

'ask' is the definition.
(I know that ask is a more specific form of demand)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for demand that I've seen before include "Ask - what the public wants" , "An imperious request made as if by right" , "Forceful request" , "Insistent request" , "Madden (anag)" .)

I've seen this clue in the Evening Standard.

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.