The most common and most likely answer to this crossword clue is the 9 letter word REMINDING
I've seen this crossword clue in The Daily Telegraph
R
E
M
I
N
D
I
N
G
Buddy explains!

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 REMINDING mean?
REMINDING verb- To cause one to experience a memory (of someone or something); to bring to the notice or consideration (of a person).
- The act by which somebody is reminded of something.