Not the king of plums! (8)
I believe the answer is:
victoria
'king of plums' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'not the' is the wordplay.
I cannot really see how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for victoria that I've seen before include "English queen" , "British queen" , "Queen and Falls" , "one wasn't amused" , "She falls in Africa" .)