The most common and most likely answer to this crossword clue is the 10 letter word PALLIATIVE
I've seen this crossword clue in The Times
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More clues leading to the result PALLIATIVE
Buddy explains!
The straight part
We know that "painkiller" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case painkiller = palliative.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 PALLIATIVE mean?
PALLIATIVE noun- Something that palliates, particularly a palliative medicine.
- Serving to palliate; serving to extenuate or mitigate.
- Minimising the progression of a disease and relieving undesirable symptoms for as long as possible, rather than attempting to cure the (usually incurable) disease.