The most common and most likely answer to this crossword clue is the 6 letter word WINNOW
I've seen this crossword clue in The Sunday Telegraph
W
I
N
N
O
W
More clues leading to the result WINNOW
Buddy explains!
The straight part
We know that "Fan" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fan = winnow.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 WINNOW mean?
WINNOW noun- That which winnows or which is used in winnowing; a contrivance for fanning or winnowing grain.
- To subject (granular material, especially food grain) to a current of air separating heavier and lighter components, as grain from chaff.
- To separate, sift, analyze, or test by separating items having different values.
- To blow upon or toss about by blowing; to set in motion as with a fan or wings.
- To move about with a flapping motion, as of wings; to flutter.