The most common and most likely answer to this crossword clue is the 11 letter word SHOT-PUTTER
S
H
O
T
-
P
U
T
T
E
R
Buddy explains!
The straight part
We know that "sportsperson using strong-arm tactics" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sportsperson using strong-arm tactics = shot-putter.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.