Last one, 10a, Understand Peru's lowest class: p?n?t?a?e. I can find words to fit, but can't see why any of them are the right answer - grateful for any help as ever.
Thankyou Sarumite. I thought of penetrate as meaning to understand, rather than to be understood - am I getting old and pedantic (or just older and more pedantic)? I've noticed one or two cases lately where I did not agree with the sense in which a word was used in the answer or clue of a crossword.