The most common and most likely answer to this crossword clue is the 8 letter word VEHEMENT
I've seen this crossword clue in Independent
V
E
H
E
M
E
N
T
More clues leading to the result VEHEMENT
- Strong macho types kept in check
- Fierce old fighter stopped by tough guys
- Forceful, macho types held in check
- Furious, means to escape across English border
- Forceful, keeping macho types in check
- Some love he-men, tough, very intense
- Hot hunks in check
- Forceful English edge into opening
- Violent English border guards let out? On the contrary
- Strong old soldier captures macho blokes
Buddy explains!

The straight part
We know that "Strong" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case strong = vehement.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 VEHEMENT mean?
VEHEMENT adjective- Showing strong feelings; passionate; forceful or intense.