Sentence:  "Of course a miracle may happen, and you may be a great painter, but you must confess the chances are a million to one against it. It'll be an awful <WSD>sell</WSD> if at the end you have to acknowledge you've made a hash of it." 
Meaning of the word marked with <WSD> tags:  An imposition, a cheat; a hoax; a disappointment; anything occasioning a loss of pride or dignity.