"Could I vaccinate you?" "Go on" (6)
I believe the answer is:
jabber
'go on' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for jabber that I've seen before include "indistinct speech" , "one that's given punch" , "Talk rapidly/excitedly" , "Rapid (foreign) talk" , "One who digs" .)