The most common and most likely answer to this crossword clue is the 8 letter word LOOSENED
I've seen this crossword clue in Independent
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More clues leading to the result LOOSENED
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 = loosened.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 LOOSENED mean?
LOOSENED verb- To make loose.
- To become loose.
- To disengage (a device that restrains).
- To become unfastened or undone.
- To free from restraint; to set at liberty.
- To relieve (the bowels) from constipation; to promote defecation.
- To create a breach or rift between (two parties).
- To sail away (from the shore).
- Having been made less tight or more relaxed.