The most common and most likely answer to this crossword clue is the 7 letter word FLANKER
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More clues leading to the result FLANKER
Buddy explains!

The straight part
We know that "rugby player" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rugby player = flanker.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 FLANKER mean?
FLANKER noun- A player who plays in the back row of the scrum.
- A wide receiver who lines up behind the line of scrimmage.
- A fortification or soldier projecting so as to defend another work or to command the flank of an assailing body.
- To defend by lateral fortifications.
- To attack sideways.