The most common and most likely answer to this crossword clue is the 8 letter word STALWART
I've seen this crossword clue in Independent
S
T
A
L
W
A
R
T
More clues leading to the result STALWART
- Reliable fellow to begin suppressing breaking of law
- Begin introducing law that’s upset faithful
- Staunch a flow evenly, opening bandages
- Strong supporter of institute introducing new law
- Show surprise about law-breaking supporter
- Committed saint with extremely abnormal verruca
- Strong law is broken in the beginning
- Dependable cooking salt applied to growth
- Committed in support of last ground offensive by terrorist leader
- Loyal from outset, accepting poor law
Buddy explains!

The straight part
We know that "loyal supporter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case loyal supporter = stalwart.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 STALWART mean?
STALWART noun- One who has a strong build.
- One who firmly supports a cause.
- One who is dependable.
- Firmly or solidly built.
- Courageous.
- Determined; staunch.