Religious leader’s endless talk (5)
I believe the answer is:
rabbi
'religious leader's' is the definition.
(I've seen this before)
'endless talk' is the wordplay.
'endless' means to remove the last letter.
'talk' becomes 'rabbit' (I've seen this before).
'rabbit' with its last letter taken away is 'RABBI'.
(Other definitions for rabbi that I've seen before include "endless waffle" , "A Jewish scholar or synagogue leader" , "Legal expert" , "Religious leader in a Jewish community" , "Sacks, for example" .)