The most common and most likely answer to this crossword clue is the 5 letter word AUXIN
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More clues leading to the result AUXIN
Buddy explains!
The straight part
We know that "It helps to stimulate growth" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it helps to stimulate growth = auxin.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 AUXIN mean?
AUXIN noun- A class of plant growth substance (often called phytohormones or plant hormones) which play an essential role in coordination of many growth and behavioral processes in the plant life cycle.