Cheap shot about writing of lecture (6)
I believe the answer is:
preach
'lecture' is the definition.
('preach' can be a synonym of 'lecture')
'cheap shot about writing' is the wordplay.
'shot' indicates anagramming the letters.
'about' indicates putting letters inside.
'writing' becomes 'r' (I've seen this in other clues**).
'cheap' with letters rearranged gives 'peach'.
'peach' enclosing 'r' is 'PREACH'.
'of' is the link.
(Other definitions for preach that I've seen before include "Give moral or religious advice" , "Lecture" , "Proclaim (religion)" , "Give a religious address" , "Proclaim (a religious message)" .)