The most common and most likely answer to this crossword clue is the 7 letter word UNWOUND
I've seen this crossword clue in The Sunday Telegraph
U
N
W
O
U
N
D
More clues leading to the result UNWOUND
Buddy explains!

The straight part
We know that "relaxed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case relaxed = unwound.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 UNWOUND mean?
UNWOUND verb- To separate (something that is wound up)
- To disentangle
- To relax; to chill out; to rest and relieve of stress
- To be or become unwound; to be capable of being unwound or untwisted.
- To undo something.
- To analyse (a call stack) so as to generate a stack trace etc.