The most common and most likely answer to this crossword clue is the 8 letter word STIMULUS
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More clues leading to the result STIMULUS
- Good sort, this person's high-class, with endless desire for encouragement
- Spark is appropriate around Scottish chimney, on reflection
- Spur Africans missing leader after mist dispersed
- Raised cases involving obstinate type lacking energy and incentive
- Stubborn type, endlessly engaged in legal actions, raised motivation
- Nudge — it’s about a Greek letter — first letter to the Guardian
- Incentive from drug carriers trading ecstasy for uranium – it’s back to front
- It produces reaction — litmus changes before its conclusion
- Something arousing? Aroused, I must cut sexual desire
- Litmus test on University’s influence
Buddy explains!

The straight part
We know that "Nudge" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nudge = stimulus.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 STIMULUS mean?
STIMULUS noun- Any external phenomenon that has an influence on a system, by triggering or modifying an internal phenomenon.
- Something external that elicits or influences a physiological or psychological activity or response.
- Anything effectively impinging upon any of the sensory apparatuses of a living organism, including physical phenomena both internal and external to the body.
- Anything that induces a person to take action.