6ac and 17ac are just what you said - look up those varieties of the first word in Chambers and you will get definitions that fit the fairly obvious word at 17ac (in an appendix) and the rather more tasty, obscure one at 6ac.
I must apologise to Doc, the editor, for suggesting that he had made an unnecessary correction. It must be thankless enough to be a crossword editor without having being unfairly blamed for errors. I was far too quick to point the finger, and am happy to set the record straight.