The most common and most likely answer to this crossword clue is the 5 plus 8 letter word THREE QUARTERS
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More clues leading to the result THREE QUARTERS
Buddy explains!

The straight part
We know that "They play rugby" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they play rugby = three quarters.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 THREE QUARTERS mean?
THREE QUARTERS adjective- Three-quarter
- Three quarters