Second right-wing bank clerk is a liar (11)
I believe the answer is:
storyteller
'a liar' is the definition.
(storyteller is a kind of liar)
'second right-wing bank clerk' is the wordplay.
'second' becomes 's' (common abbreviation).
'right-wing' becomes 'tory'.
'bank clerk' becomes 'teller' ('teller' can be a synonym of 'bank clerk').
's'+'tory'+'teller'='STORYTELLER'
'is' acts as a link.
(Other definitions for storyteller that I've seen before include "he retails pork pies" , "Dishonest retailer" , "Raconteur" , "Narrator of tale, liar" , "Narrator (possibly a liar?)" .)