With reference to 6 Down, I just wanted to also convey my unease about the answer. The clue, for
those that may be unaware, is - One who has got to
"excel" from what we hear!
Obviously, the compiler has been a numpty with
regards to this clue, and didn't think what he was doing, as the answer, NONAGENARIAN, would throw
his "excel" (XL) out, (which most of us know equates
to FORTY), and as some kind soul has already pointed out, reaching 90 years of age would mean, in Roman numerals, becomIng "XC" and not "XL".
Us mere mortals who solve these sometimes complex
clues, are ENTITLED to make mistakes, but the compilers don't have anywhere to run and hide!