The most common and most likely answer to this crossword clue is the 5 letter word LEGAL
I've seen this crossword clue in The Daily Telegraph
L
E
G
A
L
More clues leading to the result LEGAL
- Article left on stage following act?
- It's acceptable for one article to appear between lines
- Liberals inspiring revolutionary period? That’s right
- Nigella gelatinised revolting stuffing — that’s valid!
- Right on a length
- Relating to the law of gravitation originally observed in a field near Luxembourg
- Allowed American tax evader to take stage first
- It’s allowed on a lake
- The French girl, sanctioned …
- This is allowed on a lake
Buddy explains!

The straight part
We know that "Sanctioned" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sanctioned = legal.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 LEGAL mean?
LEGAL noun- The legal department of a company.
- Paper in sheets 8½ in × 14 in (215.9 mm × 355.6 mm).
- A spy who is attached to, and ostensibly employed by, an embassy, military outpost, etc.
- Somebody who immigrated lawfully.
- Relating to the law or to lawyers.
- Having its basis in the law.
- Being allowed or prescribed by law.
- Above the age of consent or the legal drinking age.
- (of paper or document layouts) Measuring 8½ in × 14 in (215.9 mm × 355.6 mm) (also legal-size).