Extras denied lead part, I suppose (3)
I believe the answer is:
yes
'extras' is the definition.
Although both the answer and definition are singular nouns, I don'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 yes that I've seen before include "Aye" , "Certainly!" , "That's 27 [RIGHT]" , "Yea" , "Agreed" .)