Deviously elect Sire Dudley (as he was historically known) (9)
I believe the answer is:
leicester
'dudley as he was historically known' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'deviously elect sire' is the wordplay.
'deviously' indicates an anagram (I've seen this in other clues).
'elect'+'sire'='electsire'
'electsire' anagrammed gives 'LEICESTER'.
Can you help me to learn more?
(Other definitions for leicester that I've seen before include "Cheese; town" , "At Richmond Palace a favourite" , "royal favourite" , "English cheese, maybe red" , "East Midlands city, home of the National Space Centre" .)