Agatha Order is mostly tied right inside (8)
I believe the answer is:
christie
But I can't explain it at all! Could you help me understand?
(Other definitions for christie that I've seen before include "'Agatha..., crime writer (8)'" , "our 1/4 Across [GOLD MEDALLIST] in 1992" , "Serial killer" , "family with lots to do?" , "Agatha ---, novelist; John ---, murderer" .)