The most common and most likely answer to this crossword clue is the 9 letter word HEAVY-SET
I've seen this crossword clue in The Times
H
E
A
V
Y
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S
E
T
More clues leading to the result HEAVY-SET
Buddy explains!
The straight part
We know that "strapping" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case strapping = heavy-set.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 HEAVY-SET mean?
HEAVY-SET adjective- (of a person) Having a large, solid, imposing bodily appearance; overweight.