Indian state upset about wrongdoing by one king of Numidia (9)

'king of numidia' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'indian state upset about wrongdoing by one' is the wordplay.
'indian state' becomes 'assam' (I've seen this in another clue).
'upset' says the letters should be written backwards.
'about' is an insertion indicator.
'wrongdoing by' becomes 'sin' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'one' becomes 'i' (Roman numeral).
'assam' backwards is 'massa'.
'sin'+'i'='sini'
'massa' enclosing 'sini' is 'MASINISSA'.

Can you help me to learn more?