The most common and most likely answer to this crossword clue is the 7 letter word OPT-OUT
O
P
T
-
O
U
T
Buddy explains!
The straight part
We know that "Decision not to take part" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case decision not to take part = opt-out.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 OPT-OUT mean?
OPT-OUT noun- The act of opting out of something
- A school or hospital that has withdrawn from local control
- A regional broadcast that other stations in the network may elect not to include.
- Of a selection, the property of having to choose explicitly to avoid or forbid something; a decision having the default option being inclusion or permission; used particularly with regard to mailing lists and advertisement.