Enjoyed doing this last weekend during a family birthday reunion in Hathersage.
Disagree that the short across answer is an abbreviation - not so in Chambers 2011 at any rate. I'm with fyellin on this one (though there's probably an abbreviation elsewhere that I haven't spotted!)
While the instructions ask us only to highlight six cells (so the grid with clashes resolved is the final grid) I'm intrigued that there is an area of the grid which contains the appropriate letters, some repeated, all contiguous.
As far as I can see there's one way of removing the six required letters which would still leave all real words (though it would top one thematic item).
The more straightforward location of the six cells would not leave real words after removal. I wonder if the original idea was to ask us to remove the cells (and if so, why change it?)
There is one other puzzle - why six cells? From the source material, I'd expect seven.