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

The straight part
We know that "One having brawn rather than brains?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one having brawn rather than brains? = meathead.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 MEATHEAD mean?
MEATHEAD noun- An ungainly, dull or stupid person; someone who is lazy, disrespectful and/or whose beliefs and philosophies clash with another.
- A large, muscular, stupid male, especially an athlete.
- A member of the Canadian Forces Military Police.