The most common and most likely answer to this crossword clue is the 7 letter word EMPOWER
I've seen this crossword clue in Independent
E
M
P
O
W
E
R
More clues leading to the result EMPOWER
- Enable soldiers to turn up, bearing military captive
- Start of employment male might authorise
- Authorise retired military engineers to lock up prisoner
- Entitle army corps to pull back holding detainee
- One way to expand MP’s permit
- Allow MP over in vessel
- Authorise military engineers to return without prisoner
- Allow no time at all for worker to rise
- Give authority to newly created peer, woman ignoring a Nationalist
- Authorise me to return pawn, not so important after the opening
Buddy explains!

The straight part
We know that "Sanction" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sanction = empower.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 EMPOWER mean?
EMPOWER verb- To give permission, power, or the legal right to do something.
- To give someone more confidence and/or strength to do something, often by enabling them to increase their control over their own life or situation.