Artist in diva upset about rhetoric, ultimately (2,5)
I believe the answer is:
da vinci
'artist' is the definition.
(I've seen this before)
'in diva upset about rhetoric ultimately' is the wordplay.
'upset' indicates an anagram.
'about' indicates putting letters inside.
'ultimately' says to take the final letters.
The last letter of 'rhetoric' is 'c'.
'in'+'diva'='indiva'
'indiva' with letters rearranged gives 'davini'.
'davini' enclosing 'c' is 'DA VINCI'.
(Other definitions for da vinci that I've seen before include "'Versatile genius of the Italian Renaissance (2,5)'" , "artist, scientist, and engineer" , "Italian inventor artist" , "Leonardo . . . painted the" , "See 13 Down" .)