Dictator of no great importance (5,6)

'no great importance' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'dictator' is the wordplay.
I cannot really see how this works, but
'dictator' could be 'tyrant' (tyrant is a kind of dictator) and 'tyrant' is found within the answer.
The remaining letters 'petty' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

'of' is the link.

Can you help me to learn more?