Crossword Genius

Tell me, is that believable? (1,3,3)

Ross

I believe the answer is:

i ask you

'is that believable?' is the definition.
(expression of disbelief)

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

(Other definitions for i ask you that I've seen before include "that's hard to credit" , "interrogator clarifies roles?" , "Can one believe it!" , "how ridiculous is that?" , "really!" .)

I've seen this clue in The Guardian.
Want a hint initially instead of a full solution? Install my app