### Clue: Insensitive sort? My dear chap, ignoring an American is dreadful (9)
### Answer: PACHYDERM 
 ### Explanation: Definition: Insensitive sort?
 **Anagram of**(… is dreadful) "My dear chap" **minus one**(ignoring an) "A"(abbrev. for "American").
Defn: …, as a result of having a thick and impervious skin.