The most common and most likely answer to this crossword clue is the 9 letter word FLATTERER
I've seen this crossword clue in The Times
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More clues leading to the result FLATTERER
- Note shorter, less singular person using flannel
- One who gives you soap and flannel
- French brother endlessly drinking coffee is 11
- Fawner primarily, the second of two queens is a bootlicker
- Female succeeding Queen’s lackey
- Sycophant is more prostrate before Queen
- Bigger monarch gaining pounds? One uses butter
Buddy explains!

The straight part
We know that "person using flannel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case person using flannel = flatterer.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 FLATTERER mean?
FLATTERER noun- One who flatters.