The most common and most likely answer to this crossword clue is the 5 letter word LANKY
I've seen this crossword clue in The Times
L
A
N
K
Y
More clues leading to the result LANKY
- Very tall new king welcomed in ballad
- Gangling city knight going over the Bluegrass State
- Thin side short of force, unknown quantity
- Scrawny neck, but no stuffing, put in place
- Tall and thin and large, awkward Yank
- Thin song about leaders of North Korea
- . Stretched in frame, blank your minds
- Left whatever king wore, it's spare
- Tall and large, clumsy yank
Buddy explains!

The straight part
We know that "Thin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case thin = lanky.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 LANKY mean?
LANKY adjective- Tall, slim, and rather ungraceful or awkward.