An unrivalled governor: unofficial supremo, then ubiquitous sovereign, primarily? (8)
I believe the answer is:
augustus
'an unrivalled governor' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'unofficial supremo then ubiquitous sovereign primarily?' is the wordplay.
'unofficial supremo then' becomes 'august' (I can't explain this - if you can you should give a lot more credence to this answer).
'primarily?' says to take the initial letters (I've seen 'primarily' mean this).
The initial letters of 'ubiquitous sovereign' is 'us'.
'august'+'us'='AUGUSTUS'
Can you help me to learn more?
(Other definitions for augustus that I've seen before include "Roman emperor, of a summer month?" , "John, say" , "one whose name was John?" , "head for Rome" , "Fort --, Scottish town" .)