One of those teaching a lesson to voter needs no introduction (6)
I believe the answer is:
lector
'one' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for lector that I've seen before include "Person reading lessons in church" , "one reads" , "Reader, esp. in church" , "Reader at certain universities" , "Hannibal - -" .)