The most common and most likely answer to this crossword clue is the 7 letter word TALKING
I've seen this crossword clue in The Times
T
A
L
K
I
N
G
Buddy explains!

The straight part
We know that "lecture" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lecture = talking.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TALKING mean?
TALKING noun- The action of the verb talk.
- To communicate, usually by means of speech.
- To discuss; to talk about.
- To speak (a certain language).
- (chiefly used in progressive tenses) Used to emphasise the importance, size, complexity etc. of the thing mentioned.
- To confess, especially implicating others.
- To criticize someone for something of which one is guilty oneself.
- To gossip; to create scandal.
- (chiefly used in progressive tenses) To influence someone to express something, especially a particular stance or viewpoint or in a particular manner.