Scholar to talk endlessly (5)
I believe the answer is:
rabbi
'scholar' is the definition.
(thesaurus)
'talk endlessly' is the wordplay.
'talk' becomes 'rabbit' (I've seen this before).
'endlessly' means to remove the last letter.
'rabbit' with its last letter taken away is 'RABBI'.
'to' is the link.
(Other definitions for rabbi that I've seen before include "Religious leader of Jewish congregation" , "Jewish learned man" , "Jewish minister" , "Sacks, for example" , "Jewish religious teacher" .)