Hectoring lecture (8)
I believe the answer is:
harangue
'hectoring lecture' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for harangue that I've seen before include "Forceful and aggressive speech" , "Exhortation" , "A lengthy vehement speech, may be abusive" , "A lengthy speech or scolding" , "Hectoring lecture" .)