The most common and most likely answer to this crossword clue is the 8 letter word BEANPOLE
I've seen this crossword clue in Independent
B
E
A
N
P
O
L
E
More clues leading to the result BEANPOLE
- One very tall European runner, say, is in front
- Very thin person employed to train runners?
- Head man from Krakow's supporter in plot
- One very tall European runner, say, is ahead
- Spare person providing support in kitchen garden
- Boycott involving East European gardening equipment
- Tall fellow
- Man catching a perch is tall and thin
- Tall thin person training runners
- Head getting European support for runner, maybe
Buddy explains!

The straight part
We know that "tall skinny person" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tall skinny person = beanpole.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 BEANPOLE mean?
BEANPOLE noun- A thin pole for supporting bean vines.
- A tall, thin person.