Notrab, it's perfectly true that Chambers' isn't the only reference, especially when it comes to geographical names, proper nouns, etc. However, if a setter uses a word that is in Chambers but a definition that is not in Chambers, that would be flagged in the preamble. This case is identical. I don't want to blow up the issue out of proportion - I see it is a flaw, but perhaps not a major flaw. But wouldn't it have been better if the other five examples had been true acronyms? There are loads to choose from so I cannot believe that would have seriously impeded grid construction. It would have been a more elegant puzzle for it in my view.