Compound of lead cured doctor's inner demon (8)
I believe the answer is:
aldehyde
'compound' is the definition.
(aldehyde is a kind of compound)
'lead cured doctor's inner demon' is the wordplay.
'cured' indicates an anagram.
'doctor's inner demon' becomes 'hyde' (Mr Hyde, alter ego of Doctor Jekyll).
'lead' with letters rearranged gives 'alde'.
'alde'+'hyde'='ALDEHYDE'
'of' is the link.
(Other definitions for aldehyde that I've seen before include "Organic compound" , "chemical" .)