Rule paid off by producing pain medication (8)
I believe the answer is:
epidural
'producing pain medication' is the definition.
I can't tell whether this definition defines the answer.
'rule paid off' is the wordplay.
'off' indicates anagramming the letters.
'rule'+'paid'='rulepaid'
'rulepaid' with letters rearranged gives 'EPIDURAL'.
'by' acts as a link.
Can you help me to learn more?
(Other definitions for epidural that I've seen before include "Anaesthetic injected into the spinal cord" , "Injection of anaesthetic into the spinal cord" , "Anaesthetic used in childbirth" , "Painkiller" .)