The most common and most likely answer to this crossword clue is the 8 letter word INFLAMES
I've seen this crossword clue in Financial Times
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More clues leading to the result INFLAMES
Buddy explains!
The straight part
We know that "Makes more passionate" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case makes more passionate = inflames.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 INFLAMES mean?
INFLAMES verb- To set on fire; to kindle; to cause to burn, flame, or glow.
- To kindle or intensify (a feeling, as passion or appetite); to excite to an excessive or unnatural action or heat.
- To provoke (a person) to anger or rage; to exasperate; to irritate; to incense; to enrage.
- To put in a state of inflammation; to produce morbid heat, congestion, or swelling, of.
- To exaggerate; to enlarge upon.
- To grow morbidly hot, congested, or painful; to become angry or incensed.