The most common and most likely answer to this crossword clue is the 4 letter word KIND
K
I
N
D
Buddy explains!

The straight part
We know that "Thoughtful/sort" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case thoughtful/sort = kind.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 KIND mean?
KIND noun- A type, race or category; a group of entities that have common characteristics such that they may be grouped together.
- A makeshift or otherwise atypical specimen.
- One's inherent nature; character, natural disposition.
- Family, lineage.
- Manner.
- Goods or services used as payment, as e.g. in barter.
- Equivalent means used as response to an action.
- Each of the two elements of the communion service, bread and wine.
- Having a benevolent, courteous, friendly, generous, gentle, liberal, sympathetic, or warm-hearted nature or disposition, marked by consideration for – and service to – others.
- Affectionate.
- Favorable.
- Mild, gentle, forgiving
- Gentle; tractable; easily governed.
- Characteristic of the species; belonging to one's nature; natural; native.