The most common and most likely answer to this crossword clue is the 7 letter word YORKIST
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More clues leading to the result YORKIST
- Historically, one preferred the house white
- Former partisan’s uniform stolen from the solver’s chest
- Richard III, say — king one encountered in strange story
- Solver’s received affection, speaking out for English partisan
- House supporter one’s gently touched, it’s said
- Supporter wearing white rose to risky caper
- Chap backing king’s first supporter of the White Rose
- See one’s trellis primarily supporting white rose
- Risky to reset a rose supporter
- Richard III?
Buddy explains!

The straight part
We know that "supporting white rose" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case supporting white rose = yorkist.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.