Ambitious taking foot off? Painkiller required (7)

I believe the answer is:

aspirin

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'painkiller required' is the definition.
I can't judge whether this definition defines the answer.

'ambitious taking foot off?' is the wordplay.
'ambitious' becomes 'aspiring' (similar in meaning).
'taking foot off?' means to remove the last letter.
'aspiring' with its final letter taken off is 'ASPIRIN'.

Can you help me to learn more?

(Other definitions for aspirin that I've seen before include "Common pain tablet" , "Anodyne" , "number" , "Headache pill" , "Pain-relieving tablet" .)

I've seen this clue in The Telegraph.

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