An east European impressed by no French emperor (8)
I believe the answer is:
napoleon
'emperor' is the definition.
(Napoleon is an example)
'an east european impressed by no french' is the wordplay.
'an' becomes 'a'.
'east european' becomes 'pole'.
'impressed by' indicates putting letters inside.
'no french' becomes 'non' ('no' in French).
'a'+'pole'='apole'
'apole' inserted into 'non' is 'NAPOLEON'.
(Other definitions for napoleon that I've seen before include "The familiar Bonaparte" , "no longer tender" , "French VIP" , "The little French general" , "Gold twenty franc piece" .)