Shut your mouth after admitting lies regularly (7)
I believe the answer is:
silence
'shut your mouth' is the definition.
('silence' can be used to tell someone to shut up)
'after admitting lies regularly' is the wordplay.
'after' becomes 'since' (I've seen this in other clues).
'admitting' is an insertion indicator.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternating letters of 'lies' are 'le'.
'since' enclosing 'le' is 'SILENCE'.
(Other definitions for silence that I've seen before include "Absence of racket" , "There's nothing heard" , "Quietness" , "'The rest is - - '(Hamlet)" , "Lack of sound" .)