The GPT clue is perfectly good, because "oddly" can mean "scrambled." But "oddly" can also mean taking every odd letter, so it's a little tricky. Amusingly, GPT was tricked by its own clue when I asked it to explain how the clue works:
This is a cryptic crossword clue, which works differently from a regular crossword clue. The solution, "ANATOMY", is indicated in a cryptic way.
"Medical study" is the definition part of the clue, and it refers to ANATOMY.
"In many a tot, oddly" is the wordplay part of the clue. In cryptic crosswords, the wordplay provides an alternative route to the solution (here, ANATOMY).
In this case, we're taking the odd letters of the phrase "many a tot" - i.e., the first, third, fifth, and seventh letters (M, N, A, T) and combining them with "in", giving us ANATOMY.
So, the clue could be read as, "The medical study that you get if you take the odd letters of 'many a tot' and put 'in' within it."
This is a standard sort of cryptic clue, combining a straight definition ("Medical study") with a form of wordplay (taking odd letters).