The most common and most likely answer to this crossword clue is the 8 letter word CHIVALRY
I've seen this crossword clue in The Daily Telegraph
C
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More clues leading to the result CHIVALRY
- Noble quality of larch, wound round with ivy
- Courtesy of chief rival wounded close to Burgundy
- Courtesy in conflict when church replaces leader
- Appalling lairy chav lacking a code of good behaviour
- Courtsey shown by Greek character to lady by railway
- Switzerland heads competition after leader’s avoided playing the knight
Buddy explains!

The straight part
We know that "playing the knight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case playing the knight = chivalry.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 CHIVALRY mean?
CHIVALRY noun- Cavalry; horsemen armed for battle.
- The fact or condition of being a knight; knightly skill, prowess.
- The ethical code of the knight prevalent in Medieval Europe, having such primary virtues as mercy towards the poor and oppressed, humility, honour, sacrifice, fear of God, faithfulness, courage and utmost graciousness and courtesy to ladies.
- Courtesy, respect and honourable conduct between opponents in wartime.
- Courteous behaviour, especially that of men towards women.
- A tenure of lands by knightly service.