The most common and most likely answer to this crossword clue is the 6 letter word MIRAGE
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More clues leading to the result MIRAGE
- I'm taken aback by anger? That's an illusion
- Silver in the dirt is an illusion
- Motorway madness? See it to believe it?
- Motorway madness? It isn't what it appears to be
- Driver’s anger on London-to-Leeds journey? It’s not real
- Optical illusion created by image moving over river
- Introductions to masters in relativity: time’s an illusion
- I’m taken aback by fashion — it’s an illusion
- Get on after skirt pulled back – that’s not what it seems
- French fighter‘s motorway madness
Buddy explains!

The straight part
We know that "It isn't what it appears to be" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it isn't what it appears to be = mirage.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 MIRAGE mean?
MIRAGE noun- An optical phenomenon in which light is refracted through a layer of hot air close to the ground, giving the appearance of there being refuge in the distance.
- An illusion.
- To cause to appear as or like a mirage.