Emperor's East European origins initially concealed by grandma (8)
I believe the answer is:
napoleon
'emperor's' is the definition.
(Napoleon is an example)
'east european origins initially concealed by grandma' is the wordplay.
'east european' becomes 'pole'.
'initially' indicates taking the first letters.
'concealed by' is an insertion indicator.
'grandma' becomes 'nan' (I've seen this before).
The initial letter of 'origins' is 'o'.
'pole'+'o'='poleo'
'poleo' inserted into 'nan' is 'NAPOLEON'.
(Other definitions for napoleon that I've seen before include "leader in France, once" , "French emperor, d.1821" , "Emperor - brandy" , "Extended nap" , "Gold twenty franc piece" .)