The most common and most likely answer to this crossword clue is the 7 letter word RECYCLE
I've seen this crossword clue in The Guardian
R
E
C
Y
C
L
E
More clues leading to the result RECYCLE
- Save on eco-friendly transport
- Repeat of Crécy? Clearly, in part
- Creatively adapt touching series of songs?
- Secrecy clearly surrounding a way to combat consumerism?
- About to get bike and make into something new
- Send for treatment here, after he falls off bike
- What Greens do on bike
- Soldiers mounting revolution in attempt to save the world?
- What Greens will do about revolution?
- Revolution by engineers to be green
Buddy explains!

The straight part
We know that "Send for treatment" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case send for treatment = recycle.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 RECYCLE mean?
RECYCLE noun- An act of recycling.
- 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.