Lover got a Roman imperator somewhat upset (9)
I believe the answer is:
inamorato
'lover' is the definition.
(I know that inamorato is a type of lover)
'got a roman imperator somewhat upset' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'upset' says the letters should be written in reverse.
'otaromani' is hidden within 'got a roman imperator'.
'otaromani' in reverse letter order is 'INAMORATO'.
(Other definitions for inamorato that I've seen before include "I Love A Lassie" , "One who's fond of" , "Beau" , "Male lover" , "He loves" .)