Paris involved in making painkiller (7)
I believe the answer is:
aspirin
'painkiller' is the definition.
(aspirin is a kind of painkiller)
'paris involved in' is the wordplay.
'involved' indicates anagramming the letters (involved can mean confusing or complex).
'paris' is an anagram of 'aspir'.
'aspir'+'in'='ASPIRIN'
'making' acts as a link.
(Other definitions for aspirin that I've seen before include "answer to pain?" , "Synthetic analgesic" , "Anti-inflammatory tablet" , "Pain-relieving tablet" , "Pain-relieving drug made in Paris" .)