Ben engaging a European, a tall thin person (8)
I believe the answer is:
beanpole
'a tall thin person' is the definition.
(I've seen this before)
'ben engaging a european' is the wordplay.
'engaging' is an insertion indicator.
'european' becomes 'pole' (Pole is an example).
'ben' enclosing 'a' is 'bean'.
'bean'+'pole'='BEANPOLE'
(Other definitions for beanpole that I've seen before include "No, be pale if as tall and thin as this" , "Plant support - thin person" , "Tall thin person - where runners are found?" , "tall skinny person" , "Runners depend on this" .)