The most common and most likely answer to this crossword clue is the 10 letter word LINEBACKER
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Buddy explains!
The straight part
We know that "American football player" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case american football player = linebacker.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 LINEBACKER mean?
LINEBACKER noun- The defensive players who are in position behind the defensive linemen and in front of the safeties and cornerbacks and whose principal responsibilities are to tackle runners and to defend against shorter passes