New ginger nuts extremely brittle with an indefinable quality (12)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

New ginger nuts extremely brittle, with an indefinable quality *(GINGER NUTS + B <rittl> E ); “extremely” means first and last letters only are used in anagram, indicated by “new”; e.g. a genre-busting novel is one that is hard to classify in a generally accepted genre