The most common and most likely answer to this crossword clue is the 9 letter word EXTENUATE
I've seen this crossword clue in Independent
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Buddy explains!

The straight part
We know that "Make light of" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case make light of = extenuate.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 EXTENUATE mean?
EXTENUATE verb- To lessen; to palliate; to lessen or weaken the force of; to diminish the conception of, as crime, guilt, faults, ills, accusations, etc.
- To make thin or slender; to draw out so as to lessen the thickness.
- To become thinner.
- To lower or degrade; to detract from.