"De nada" means (literally) that there's nothing to be thankful about. "No hay nada que agradecer". It's semantically similar to "not at all", but it can also be correctly translated to "You're welcome".
See Fred's point: could read as double def.
"cerge", missing in Chambers 2014 except as "cierge - see cerge", popped up in this week's Listener, MamyaLynne.
For what it's worth, I don't think the setter chose 'handbag' because of the - let's face it - hardly well-known name. As someone said on FB - "the best bags I've never heard of".
Perhaps Tim Moorey will grace us with his presence & set the record straight, but until then, I'm with Mamya on this :-)