Extremely knavish career by communist playing the communist reformer (10)
I believe the answer is:
khrushchev
'the communist reformer' is the definition.
The definition suggests a singular noun which matches the answer.
'extremely knavish career by communist playing' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'career' becomes 'rush' (career can mean to run or rush around).
'by communist playing' becomes 'chev' (I can't justify this - if you can you should believe this answer much more).
'knavish' with its centre removed is 'kh'.
'kh'+'rush'+'chev'='KHRUSHCHEV'
Can you help me to learn more?
(Other definitions for khrushchev that I've seen before include "Soviet premier, 1958-64" , "Nikita -, former USSR premier" , "Cold War Soviet leader" , "Kremlin's leader" .)