Endless hypocrisy followed by stern frankness (7)
I believe the answer is:
candour
'frankness' is the definition.
('candour' can be a synonym of 'frankness')
'endless hypocrisy followed by stern' is the wordplay.
'endless' means to remove the last letter.
'hypocrisy' becomes 'cant' (I've seen this before).
'followed by' is a charade indicator (letters next to each other).
'stern' becomes 'dour'.
'cant' with its last letter removed is 'can'.
'can'+'dour'='CANDOUR'
(Other definitions for candour that I've seen before include "Artlessness" , "Frankness, openness" , "show frankness" , "telling it like it is" , "'Frankness, honesty (7)'" .)