The most common and most likely answer to this crossword clue is the 3 letter word PAH
I've seen this crossword clue in Financial Times
P
A
H
More clues leading to the result PAH
Buddy explains!

The straight part
We know that "I’m disgusted" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case i’m disgusted = pah.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PAH mean?
PAH interjection- Used to express distaste, disgust or outrage.
- Father, papa.
- Grandpa, grandfather.
- A fortified Maori settlement of pre-European and early European times
- An unfortified Maori village or settlement; a kainga