Pills for nuisance assassins (11)

I believe the answer is:

painkillers

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'pills' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps there's an association between them I don't understand?

'nuisance assassins' is the wordplay.
'nuisance' becomes 'pain' (synonyms).
'assassins' becomes 'killers' (I can't justify this - if you can you should give a lot more credence to this answer).
'pain'+'killers'='PAINKILLERS'

'for' acts as a link.

Can you help me to learn more?

I've seen this clue in The Mirror.

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