About 100 before end of day stick to processing waste (9)
I believe the answer is:
recycling
'processing waste' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
'about 100 before end of day stick to' is the wordplay.
'about' becomes 're' (regarding**).
'r00' becomes 'c' ('C' can be a synonym of 'r00').
'before' is a charade indicator (letters next to each other).
'end of' indicates one should take the final letters.
'stick to' becomes 'cling' (I've seen this before).
The last letter of 'day' is 'y'.
're'+'c'+'y'+'cling'='RECYCLING'
Can you help me to learn more?
(Another definition for recycling that I've seen is " Activity of green".)