Jargon, endless jargon by Tory leader (5)
I believe the answer is:
argot
'jargon' is the definition.
('argot' can be a synonym of 'jargon')
'endless jargon by tory leader' is the wordplay.
'endless' means to look at the middle letters.
'by' says to put letters next to each other.
'tory leader' becomes 't' (I've seen this in other clues).
The middle of 'jargon' is 'argo'.
'argo'+'t'='ARGOT'
(Other definitions for argot that I've seen before include "Patois, vernacular" , "Kind of slang" , "Talk of thieves" , "secret language" , "Jargon - patois" .)