The most common and most likely answer to this crossword clue is the 10 letter word REFRACTION
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The straight part
We know that "bending of light" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bending of light = refraction.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 REFRACTION mean?
REFRACTION noun- The turning or bending of any wave, such as a light or sound wave, when it passes from one medium into another of different optical density.
- The degree to which a metal or compound can withstand heat