Clue: Looking up 109 kg messenger, one of 18 13 down 29 26 across (8,4)
Answer: MARGARET PAGE
Explanation: Definition: one of 18 13 down 29 26 across
Reverse of TERAGRAM (1012 grams, or 109 kg) + PAGE (messenger). The original version didn't show the superscript, so it just read 109 kg, which was a bit confusing.. Another Merry Wife of Windsor