The most common and most likely answer to this crossword clue is the 10 letter word RELINQUISH
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The straight part
We know that "Release" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case release = relinquish.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 RELINQUISH mean?
RELINQUISH verb- To give up, abandon or retire from something. To trade away.
- To let go (free, away), physically release.
- To metaphorically surrender, yield control or possession.
- To accept to give up, withdraw etc.