Challenging (7)

I think it could be either:

Which length description are you looking for?:

defiant

'challenging' is the definition.
(similar in meaning)

This is all the clue.

(Other definitions for defiant that I've seen before include "Openly resistant" , "Unyielding" , "showing teeth!" , "Uncooperative" , "Boldly resistant -- fainted (anag)" .)

I've seen this clue in The Telegraph, the Evening Standard and The Independent.

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.