Meursault, I certainly wouldn't want to fall out over the minutiae of clues. We can have disagreements about interpreting language and/or Chambers entries without getting into a row. I don't think a particular meaning given in Chambers should be taken in an all-inclusive sense if it's not used in that way. In this case the examples given in Chambers' second entry all use the meaning of 'beyond' rather than physical containment. However, I do accept that some of the examples given in the third entry (the prefix) support the idea of enclosure, so I'm happy withdraw my reservation about it.
I wasn't trying to nitpick, anyway. I just enjoy parsing clues particularly imaginative or unconventional ones. Cryptic clues exploit ambiguities in language. Sometimes they stretch things a bit too far and I wondered if this was one such example.