Tall thin person (8)
I believe the answer is:
beanpole
'tall thin person' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for beanpole that I've seen before include "Man of unimpressive physique" , "Tall thin person - where runners are found?" , "pea stick" , "No, be pale if as tall and thin as this" , "runner climbing here" .)