The most common and most likely answer to this crossword clue is the 9 letter word RECYCLING
I've seen this crossword clue in The Guardian
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More clues leading to the result RECYCLING
Buddy explains!
The straight part
We know that "16 activity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case 16 activity = recycling.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 RECYCLING mean?
RECYCLING verb- To break down and reuse component materials.
- To reuse as a whole.
- To collect or place in a bin for recycling.
- To be recycled.
- To discard into a recycling bin.
- The practice of sorting and collecting waste materials for new use.
- Those materials culled for recycling.