The most common and most likely answer to this crossword clue is the 7 plus 2 letter word LIGHTEN UP
I've seen this crossword clue in The Daily Telegraph
L
I
G
H
T
E
N
U
P
More clues leading to the result LIGHTEN UP
- Become cheerful, helping out in a mess — nothing to lose
- Unwind the flexes with plug in
- 508reject play on words? Relax!
- Unwind fuse in the plug
- Reduce burden at university to become more relaxed
- Went inside, wreathed in smoke, to relax
- Stop worrying about length, I got aroused
- To calm down, use lift at college
- Relax, having forced in the plug
Buddy explains!
The straight part
We know that "To calm down" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to calm down = lighten up.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.