Form of madness, say, associated with sultanate the reverse of excellent (8)
I believe the answer is:
egomania
'form of madness' is the definition.
'egomania' can be an answer for 'form' (I have seen 'form of narcissism' mean 'egomania' so perhaps 'form' could also mean 'egomania'). I am unsure of the 'of madness' bit.
'say associated with sultanate the reverse of excellent' is the wordplay.
'say' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'associated with' means one lot of letters go next to another.
'sultanate' becomes 'oman' (I've seen this before).
'the reverse of' says the letters should be written in reverse.
'excellent' becomes 'ai' (resembles 'Ao', old-fashioned term for excellent).
'ai' back-to-front is 'ia'.
'eg'+'oman'+'ia'='EGOMANIA'
Can you help me to learn more?
(Other definitions for egomania that I've seen before include "Obsessive self-absorption" , "Thinking of oneself" , "Feeling very self-conscious" , "self-centred obsession" , "Abnormally excessive opinion of oneself, quite mad" .)